Zeitschrift fur induktive Abstammungs und Vererbungslehre; Supplement 2, 1928
Differential Polyploidy in the Genus Rosa L.
C. C. Hurst

1932 notes are from: Embryo-sac Formation in Diploid and Polyploid Species of Rosae
Proc. Roy. Soc. London Series B. Biol. Sci.; 109:126-148 1932


A Septet Characters
(Diagnostic specific characters in black type)

Stems: pivotal, scandent to arcuate, stoutly armed, smooth, glabrous or apex hairy, eglandular or apex glandular setigerous.

Branches: elongated, sinuous, recurved, stoutly armed, smooth, glabrous or apex hairy, eglandular or apex glandular setigerous.

Prickles: uniform, stout dilated, upper hooked to inclined, alternate or subgeminate, upper sparsely scattered (1-4 nodal) or crowded (5-8 nodal), glabrous or hairy, eglandular or glandular.

Leaves: solitary, 3-5 or 5-7 or 7-9 foliate, persistent or deciduous.

Stipules: uniformly narrow, adnate ligulate persistent or free linear deciduous, hairy or glabrous, glandular or eglandular, auricles acuminate or acute, margins reflexed, gland-ciliate, entire to denticulate or dentate or laciniate.

Petioles: prickly with stout curved pricklets, hairy or glabrous, eglandular or glandular or glandular setose.

Leaflets: large (5-10 cm long) or middle-sized (3-5 cm long) or small (1-3 cm long), base rounded or narrowed, oval to elliptical or ovate to lanceolate, apex acuminate to cuspidate or acute, to mucronate coriaceous or sub-coriaceous, coarsely or finely serrated, teeth shallow, simple or irregular or compound, eglandular or glandular, green or glaucous above, glaucous or green beneath, hairy or glabrous above, hairy or glabrous beneath, eglandular or glandular above, eglandular or glandular beneath.

Inflorescence: compound, corymbose or paniculate, on erect branchlets, 1-100 or 1-24 or 1-12 or 1-6 or 1-3 flowered.

Bracts: narrow, linear or lanceolate, long or short pointed, hairy or glabrous, glandular or eglandular, margins gland-ciliate, entier or denticulate or laciniate, caducous or sub-persistent.

Pedicles: long (2-3 cm) or short (1-2 cm), glabrous or hairy, glandular or eglandular.

Sepals: 5, reflexed in flower and fruit, (rarely spreading or erect), early or late deciduous, outer ovate or lanceolate, longer or shorter than the petals, long or short or leaf pointed, pinnate (4-6 large pinnae) or pinnulate (1-2 small pinnae), dorsal glabrous or hairy, eglandular or glandular or glandular setose.

Petals: 5, with Musk Rose fragrance, creamy white (rarely creamy yellow) or rose pink, dorsal glabrous or hairy, margins eglandular.

Disk: broad and incrassate, orifice contracted (0.5-1 mm), flat or mamelonic or conical.

Styles: elongated (5-10 mm) and exserted beyond disc (2-8 mm) in connate or loose column, filiform, glabrous or hairy.

Fruits: late ripening, persistent, globose to ovoid or turbinate to obovoid or oblong to ellipsoid, red or orange, erect or cernuous, glabrous or hairy, eglandular or glandular, achenes 3-4 tiered basiparietal.

AA Diploid Roses

The AA diploid Roses have the A septet characters enumerated above associated with 14 chromosomes (two A septets) in the nuclei of their somatic cells and 7 chromosomes (one A septet) in their male and female gametes. The following is a list of the AA diploid Roses whose chromosomes and characters have been studied in numerous varieties of the subspecies which are arranged in the order of their geographical distribution from West to East in the temperate and tropical regions of the northern hemisphere from Western Europe, N. Africa and Asia to the Western and Eastern States of North America.

Rosa arvensis Huds. (1762): West, Central and South Europe
R. sempervirens L. (1753): Mediterranean, South Europe and North Africa
R. moschata Herrm. (1762): East Pyrenees to Sicily, Madeira and North Africa
R. phoenicia Boiss. (1849): Enos and Gallipoli to Cyprus and Western Syria
R. abyssinica R. Br. (1814): mountains of Abyssinia and South Arabia
R. Pissarti Carr. (1880): Caspian Sea to the mountains of South Persia
B. Brunoni Lindl. (1820): Afghanistan, Himalayas to Sze-chwan China
R. Leschenaultiana Wight et Arnott (1834): mountains of South India
R. longiscuspis Bertol. (1861): East Bengal India to Sze-chwan China
R. gigantea Coll. (1888): Manipur to Shan States Burma and South Yun-nan China
R. soulieana Crép. (1896): North Yun-nan to West Sze-chwan China
R. Helenae Rehdr. et Wils (1915): West Hu-peh China
R. Rubus Lév. et Van. (1908): West Sze-chwan to Kwei-chow and West Hu-peh China
R. Gentiliana Lév. et Van. (1908): East Sze-chwan to Fu-kien China
R. laevigata Michx. (1803): West Hu-peh to Formosa
R. Banksiae Ait. (1811): Sze-chwan to West Hu-peh China
R. microcarpa Lindl. (1820): West Sze-chwan to Che-kiang and Kwei-chow to Fu-kien China
R. chinensis Jacq. (1768): North West Sze-chwan to West Hu-peh China
R. anemoneflora Fortune (1847): Fu-kien China
R. cathayensis Rehdr. et Wils. (1915): West Sze-chwan and Kan-su to Fu-kien China
R. multiflora Thunb. (1784): Korea and Japan
R. Wichuraiana Crép. (1886): Korean Archipelago and Japan
R. Luciae Franch. et Rochebr. (1875): Japan
R. Watsoniana Crép. (1888): Hort. Japan
R. rubifolia Ait. (1811): Nebraska to Texas, Georgia and Ontario North America
R. setigera Michx. (1803): Kansas to Florida and North Carolina North America

Several new undescribed subspecies form China found at Kew and Cambridge.

With rare exceptions the diploid Roses above and their varieties and forms have in common the specific characters peculiar to the A septet of chromosomes. They differ from one another in major alternative characters, but as a whole they intergrade and are linked up with one another through these same major alternative characters and also through the minor alternative characters which constitute their heterozygous varieties. They also differ from one another in their habitats and range of distribution in the tropical and temperate regions of the Northern Hemisphere, in some cases they overlap while in others they are distinctly isolated from one another. So far as they have been tested genetically they are fully fertile in F1 and F2 when bred inter se and natural crosses are frequently found in the overlapping areas: genetical crosses between those that are widely isolated e.g. European and Chinese are as fully fertile as those which overlap e.g. European. On these grounds the diploid Roses above may be regarded as geographical sub-species of one large and widely distributed species, with the septet formula AA, under the selected oldest name Rosa sempervirens L. (em.). [Hurst later dropped this attempt to rename all the species as sub-species, and I have shortened the names accordingly. Thus R. sempervirens sub-sp. chinensis becomes the more familiar R. chinensis.]


B Septet Characters
(Diagnostic specific characters in black type)

Stems: pivotal or stoloniferous, inclined, rigid, densely prickly, bristly or smooth, glabrous, glandular or eglandular.

Branches: rigid and short-noded, right angled, prickly, bristly or smooth, glabrous, glandular or eglandular.

Prickles: uniform or dimorphic, stilettiform or compressed alate or both, glabrous, eglandular, upper paired infrastipular spreading ascending, lower densely scattered.

Leaves: 7-11 or 11-19 foliolate, crowded in axillary tufts, deciduous.

Stipules: uniform, flat, narrowed to base, adnate persistent, hairy or glabrous, glandular or eglandular, auricles acute, margins entire or denticulate, gland-ciliate or eglandular.

Petioles: sparsely or not prickly, hairy or glabrous, glandular or eglandular.

Leaflets: small to minute (less than 2 cm long), orbicular to oval or oval to elliptical, base and apex rounded with broad apical teeth and entire basal margins, teeth simple or compound, eglandular or glandular, firm texture, green or glaucous above, glaucous or green beneath, glabrous or pubescent above, serceous or glabrous beneath, eglandular or glandular above, glandular or eglandular beneath.

Inflorescence: flowers solitary (rarely 1-4 flowered), wreathed on short lateral branches.

Bracts: absent or rare, elliptical, acute, persistent, hairy or glabrous, glandular or eglandular; margins entire, eglandular.

Peduncles: long (2-3 cm) or short (1-2 cm) hairy or glabrous, glandular or eglandular, apex often broad or decurrent and fleshy in fruit.

Sepals: 4 or 5, shorter than petals, erect and convergent in fruit, persistent or calyx disk and neck deciduous, outer ovate or lanceolate, entire, acute or cuspidate or leaf pointed, dorsal hairy or glabrous glandular or eglandular.

Petals: 4 or 5, with fruity to foetid scent, ivory white or sulphur yellow or carmine pink, dorsal glabrous, margins eglandular.

Disk: narrow and thin, orifice circ. 2mm, flat.

Styles: few (5-20), exserted beyond disc (1-3 mm) or included, free and loose, contorted, hairy.

Fruits: early ripening, deciduous, sub-erect or pendent, globose or urceolate with neck or pyriform decurrent, black or red or orange-coloured, glabrous or hairy, glandular or eglandular, achenes few, 2-3 tiered basi-parietal or basilar.

BB Diploid Roses

The BB diploid Roses hae the B septet characters enumerated above associated with 14 chromosomes (two B septets) in the nuclei of their somatic cells and 7 chromosomes (one B septet) in their male and female gametes. The following is a list of the BB diploid Roses whose chromosomes and characters have been studied in numerous varieties of the subspecies which are arranged in the order of their geographical distribution from West to East in Asia and North America, none having been found in Europe, Africa or E. North America.

R. cabulica Boiss. (1872): E. Afghanistn, Waziristan to Baluchistan
R. Ecae Aitch. (1880): S. Russian Turkestan and E. Afghanistan
R. Webbiana Wall. (1839): S. Russian Turkestan, E. Afghanistan, W. Himalayas to W. Tibet
R. sericea Lindl. (1820): E. Himalayas, S. Thibet and Upper Burma
R. omeiensis Rolfe (1912): W. China from Yun-nan to Kan-su and Shen-si
R. sertata Rolfe (1913A): W. and Central China
R. Willmottiae Hemsl. (1907): W. Sze-chwan, China
R. Hugonis Hemsl. (1905): W. Sze-chwan to Shen-si, China
R. xanthina Lindl. (1820): Shan-si, N. China
R. gymnocarpa Nutt. (1840): California to Montana and British Columbia

The diploid Roses above and their varieties and forms have in common the specific characters peculiar to the B septet of chromosomes. They differ from one another in major alternative characters but intergrade and are linked up with one another in both major and minor characters. They are fully fertile inter se so far as tested genetically. Their habitats and range of distribution are different though restricted to Central Asia and W. North America and they may be regarded as geographical sub-species of one species with the septet formula BB, under the selected oldest name Rosa sericea Lindl. (em.).


C Septet Characters
(Diagnostic specific characters in black type)

Stems: clumped or stoloniferous, thickset, densely or sparsely prickly, densely or sparsely glandular setigerous, downy or glabrous.

Branches: spreading, tortuous, densely or sparsely prickly, densely or sparsely glandular setigerous; downy or glabrous, branchlets sub-suffruticose.

Prickles: verruculate to setae, very unequal, upper scattered and paired infrastipular, lower scattered, dense or sparse; downy or glabrous, glandular or eglandular.

Leaves: 5-7 or 7-9 foliolate, terminal and crowded on surface of bush, early deciduous.

Stipules: broad, upper dilated, sub-amplexicaul, adnate persistent, hairy or glabrous, glandular or eglandular, auricles acute or obtuse, margins gland-ciliate, undulate, entire or subdentate.

Petioles: prickly or not prickly, hairy or glabrous, glandular setaceous or glandular or eglandular.

Leaflets: large (5-10 cm long) or middle-sized (3-5 cm long), oval to elliptical or elliptical to oblong, apex obtuse or acute, coarsely serrated, teeth simple and gland tipped, thick, rugose or smooth, green or glaucous above, green or glaucous beneath, hairy or glabrous above, hairy or glabrous beneath, eglandular above, glandular or eglandular beneath.

Inflorescence: flowers few (1-4) (rarely 5-10 on surculi) terminal on surface of bush.

Bracts: sub-amplexicaul, oval to orbicular, obtuse or acute, persistent; hairy or glabrous, glandular or eglandular, margins sparsely gland ciliate, undulate dentate.

Pedicles: long (2-3 cm) or short (1-2 cm), hairy or glabrous, eglandular or glandular or setose aciculate.

Sepals: 5, outer long, entire, leaf-pointed, ovate or lanceolate or triangular: coronate in fruit, persistent or sub-persistent: dorsal downy or glabrous, eglandular or glandular or setose aciculate.

Petals: 5, with Old Rose fragrance, rose or crimson or white, dorsal glabrous, margins glandular or eglandular.

Disk: narrow and thick, orifice 2-3 mm, convex.

Styles: included, many (50-100), free and fascicled, crowded in curved sheaf, hairy.

Fruits: persistent, cernuous or pendent, depressed globose or globose or ovoid, red or orange or brown red, glabrous, eglandular or glandular or setose aciculate; achenes many 2-3 tiered mamelonic and parietal.

CC Diploid Roses

The CC diploid Roses have the C septet characters enumerated above associated with 14 chromosomes (Two C septets) in the nuclei of their somatic cells and 7 chromosomes (one C septet) in their male and female gametes. The following is a list of the CC diploid Roses whose chromosomes and characters have been studied and the sub-species are arranged in the order of their geographical distribution from West to East in E. Asia and E. North America, none having been found in Europe, Africa, W. Asia or W. North America

Rosa rugosa Thunb. (1784): Korea to Sakhalin and Japan (Specimens from Kamchatka have been erroneously placed to this species by authors and it is a doubtful native of this region.)
R. coruscans Waitz (1822): Japan to Sakhalin.
R. nipponensis Crép. (1875): Japan (non R. acicularis nipponensis auct.).
R. nitida Willd. (1809): Conecticut to Newfoundland E. North America.

Two undescribed subspecies of unknown habitat found ad Kew and Albury.

The diploid Roses above and their varieties and forms have in common the specific characters peculiar to the C septet of chromosomes. They differ from one another in major alternative characters and minor characters. Their range of distribution is different though restricted, the first three being confined to Japan and the Sea coasts of the opposite mainland while the fourth is confined to the North Eastern coast of North America, and they may be regarded as geographical sub-species of one species with the septet formula CC, under the oldest name Rosa rugosa Thunb. (em.). [CybeRose note: Erlanson identified a specimen of R. rugosa reportedly from Alaska.]


D Septet Characters
(Diagnostic specific characters in black type)

Stems: rhizomatous, erect, slender, sparsely prickly or unarmed above, prickly or sparsely prickly below, smooth glabrous, eglandular; cinnamon or green bark.

Branches: virgate, acute-angled, sparsely prickly or unarmed, smooth, glabrous, eglandular, erect or pendulous.

Prickles: slender, curved subulate to straight aciculate, upper paired infrastipular to single infrastipular to none or absent, lower densely or sparsely scattered, glabrous, eglandular.

Leaves: 5-7 or rarely 7-9 foliolate, terminally tufted, upper deciduous, lower caducous.

Stipules: dimorphic (lower narrow and upper dilated), flat to convolute, longly adnate, hairy or glabrous, glandular or eglandular, auricles acuminate or acute or obtuse, margins entire to denticulate or undulate dentate, glandular ciliate or eglandular.

Petioles: base short, prickly or not prickly, hairy or glabrous, glandular or eglandular.

Leaflets: middle-sized (3-5 cm long) or small (1-3 cm long), obovate to oblanceolate or oval to elliptic-lanceolate, apex obtuse or acute, base elliptical or cuneate, margins undulate, coarsely or finely serrated, teeth simple or compound eglandular or glandular, upper teeth deep; thin texture, green or glaucous above, glaucous or green beneath, glabrous or hairy above, hairy or glabrous beneath, eglandular above, eglandular or glandular beneath.

Inflorescence: sub-involucrate, scattered in axiliary or terminal tufts, flowers few (1-3) or corymbose (1-9).

Bracts: concave oval, acuminate or acute or obtuse, persistent, crowded and leafy, glabrous or hairy, eglandular or glandular; margins undulate, eglandular or gland-ciliate, denticulate or dentate.

Pedicles: short (0.5-2 cm), glabrous or hairy, eglandular or glandular or glandular hispid.

Sepals: 5, outer long (2-3 cm) or short (1-2 cm) caudate, ovate or lanceolate or triangular, acuminate or leaf pointed, entire or pinnulate (1-4 small pinnae); spreading or erect in fruit, thin, apices deciduous, bases persistent or deciduous; dorsal glabrous or hairy, eglandular or glandular or glandular hispid.

Petals: 5, with spice fragrance, mauve pink or carmine, dorsal glabrous, margins eglandular.

Disk: obscure, orifice wide (3-4 mm).

Styles: short (2-4 mm), included below disc, straight, stout above, free, tomentose.

Fruits: rapid ripening, walls thin with hollow upper chamber, globose or ovoid urceolate or pyriform, erect or sub-erect, red, glabrous or hairy, eglandular or glandular or glandular hispid. Achenes 2-3 tiered basi-parietal or basilar.

DD Diploid Roses

The DD diploid Roses have the D septet characters enumerated above associated with 14 chromosomes (two D septets) in the nuclei of their somatic cells and 7 chromosomes (one D septet) in their male and female gametes. The following is a list of the DD diploid Roses, whose chromosomes and characters have been studied in numerous varieties of the subspecies which are arranged in the order of their geographical distribution from West to East in Europe, Asia and North America.

R. cinnamomea L. (1759) (non L. 1753): N.W. and Central Europe (Alpine) to the Caucasus and Persia
R. davurica Pall (1784): Mongolia, N. China to Manchuria
R. Marlettii Lev. (1910): Sakhalin
R. pisocarpa A. Gray (1872): California to Idaho and British Columbia
R. Woodsii Lindl. (1820): British Columbia to W. Texas, N. Dakota and Saskatchewan Canada
R. Fendleri Crép. (1876): British Columbia to Arizona and Chihuahua Mexico, and E. to Minnesota USA
R. foliolosa Nutt. (1840): Texas to Oklahoma and Arkansas USA
R. carolina L (1753) (non L. 1762): Texas to Wisconsin and Maine to Florida USA
R. blanda Ait. (1789): Manitoba Canada to N. Dakota, Missouri, Michican, Pennsylvania to Anticosti Canada

Several new subspecies raised at Burbage from seeds collected in North America

The diploid Roses above and their varieties and forms have in common the specific characters peculiar to the D septet of chromosomes. They differ from one another in major alternative characters but intergrade and are linked up with one another in both major and minor characters. They also differ from one another in their habitats and range of distribution which includes a more or less continuous area in the N. temperate regions of the Northern Hemisphere. In North America where they are more numerous, and frequently overlap, several natural crosses have been reported (Rydberg 1918). On these grounds the diploid Roses above may be regarded as sub-species of one large and widely distributes species with the septet formula DD, under the oldest name Rosa Carolina L. (1753) (em.).


E Septet Characters
(Diagnostic specific characters in black type)

Stems: sub-pivotal, straight and cany, prickly or rarely prickly, bristly or bristly below or smooth, glabrous, eglandular or rarely glandular.

Branches: secondary (branchlets) subcernuous and subheliotropic, prickly or rarely prickly, bristly or smooth, glabrous, eglandular or rarely glandular.

Prickles: pugioniform ascending, infrastipular or none above, sparsely verticillate or rare below, glabrous, eglandular.

Leaves: distant, 7-9 foliolate, sinuous, deciduous with caducous leaflets.

Stipules: uniform, shortly adnate, base turgid and auricles dilated, hairy or glabrous, eglandular or glandular, auricles acuminate or acute, margins entire, gland-ciliate.

Petioles: base long, prickly or obscurely prickly, downy or glabrous, glandular or eglandular.

Leaflets: distant, large (5-10 cm long) or small to middle-sized (2-5 cm long), oval to elliptic or elliptic to oblong, base and apex narrowed; coarsely or finely serrated; teeth simple or irregular or compound, eglandular or glandular veins prominent and sub-parallel; soft and tough, glaucous or green above, glaucous or green beneath, hairy or glabrous above, hairy or glabrous beneath, eglandular or glandular above, glandular or eglandular beneath.

Inflorescence: flowers few (1-2) or rarely corymbulose (3-9), heliotropic on sub-cernuous branchlets.

Bracts: lanceolate to ovate acuminate, sub-persistent, hairy or glabrous, glandular or eglandular, margins eglandular or glandular, subentire or sub-dentate.

Pedicles: long (2-4 cm) or short (1-2 cm) hairy or glabrous, glandular or glandular hispid.

Sepals: 5, outer long caudate, leaf-pointed, entire, lanceolate or ovate or triangular; erect and connivent in fruit, persistent with convex fleshy base forming rim of receptacle; dorsal hairy, or glabrous glandular or glandular hispid or eglandular.

Petals: 5, with faint fragrance, carmine rose or shell pink or blush white, dorsal glabrous, margins eglandular.

Disk: broad and thin, orifice narrow (1-2 mm) concave in fruit.

Styles: elongated (6-12 mm) included below rim or rarely exserted beyond disc, few (10-30), erect, stout, free and close, hairy.

Fruits: elongated, ellipsoid with neck and rim or urceolate with neck and rim, pendulous or cernuous oblique, red, glabrous, glandular hispid or glandular or eglandular, achenes few and large, 1-4 tiered basi-parietal.

EE Diploid Roses

The EE diploid Roses have the E septet characters enumerated above associated with 14 chromosomes (two E septets) in the nuclei of their somatic cells and 7 chromosomes (one E septet) in their male and female gametes. The following is a list of the EE diploid Roses, whose chromosomes and characters have been studied in numerous varieties of the subspecies which are arranged in the order of their geographical distribution from West to East in India and China, none having been found in Europe, Africa, N. or W. Asia or N. America.

R. macrophylla Lindl. (1820): Himalaya from Kashmir to Bhutan
R. corymbulosa Rolfe (1914): W. Hu-peh, Central China
R. Giraldii Crép. (1897): W. Sze-chwan to W. Hu-peh and Shen-si, Central China
R. elegantula Rolfe (1916): E. Sze-chwan, Central China
R. persetosa Rolfe (1913B): Central China

Two new subspecies from China found at Kew

The diploid Roses above and their varieties and forms have in common the specific characters peculiar to the E septet of chromosomes. They differ from one another in major alternative characters but intergrade and are linked up with one another in both major and minor characters. They also differ from one another in their local habitats and range of distribution though all are confined to the Himalaya and Central China, on these grounds the diploid Roses above may be regarded as sub-species of one small and comparatively restricted species with the septet formula EE under the oldest name Rosa macrophylla Lindl. (em.).


The specific characters of each septet are homozygous and common to all the individuals of each of the 5 diploid septet species AA, BB, CC, DD and EE (where each letter represents a gametic septet of chromosomes). Some of the specific characters are morphological and taxonomic while others are physiological and functional. Some of the specific characters of a septet are diagnostic, being peculiar to the septet, while others are not diagnostic, being also present in other septets though not in all.

The sub-specific characters of each septet are homozygous and common only to the individuals of each of the sub-species of the 5 diploid septet species, and represent major alternative characters present in the septet, some sub-species carry one major alternative character while others carry the other resulting in various combinations. These sub-species represent geographical or for the most part isolated local races of the diploid species and seldom grow together in a single area. In this sense they may be said to be specially "adapted" to their environment.

The remaining varietal and formal characters of each septet represent the minor alternative characters present in the septet. Some varieties carry one minor alternative character while others carry the other resulting in various combinations. Varietal characters however differ from sub-specific and specific characters in so far as they may be either homozygous or heterozygous while specific and sub-specific characters are always homozygous. When varietal characters are heterozygous their genes segregate in Mendelian fashion and give rise to various combinations and recombinations by natural intercrossings and selfings in the same area. Further these varietal characters (with certain specific modifications) are more or less common alike to all the 5 diploid septet species and their sub-species, thus giving rise to the phenomenon of "parallel variation".


Polyploids

Two distinct kinds of polyploids have been found in the genus:

1. Duplicational Polyploid Varieties of the diploid species, in which the septets of chromosomes have been duplicated and whose chromosomes are often trivalent or quadrivalent in synapsis. These varieties are specifically identical with their diploid species, so that the septet formula of a tetraploid variety of the species AA is AAAA in chromosomes and characters.

2. Differential Polyploid Species in which the septets of chromosomes are differential and whose chromosomes are either bivalent or bivalent and univalent in synapsis. These are distinct species differing from one another by one or more differential septets of chromosomes and characters so that the septet formula of one tetraploid species is AABB while another tetraploid species is CCDD and so on.

1. Duplicational Polyploid Varieties

So far 21 duplicational polyploid varieties have been found in the genus, 5 tetraploids and 16 triploids, and all are cultivated forms that have arisen in gardens. None has yet been found in a wild state.

a) Tetraploid Varieties (n = 14m, 14f)

Three of these tetraploid varieties are garden forms of the wild diploid species AA, (R. sempervirens L. (em.)) having the specific characters of the A septet of chromosomes and the septet formula AAAA: two of these belong to the group of odorata (Sweet) while the other belongs to the sub-species chinensis (Jacq.) and all three are seedlings which appeared in France, Ireland and Sweden in 1853, 1913 and 1921 respectively. The fourth tetraploid variety is a garden form of the diploid species DD, (R. carolina L. (1753) (em.)) having the specific characters of the D septet of chromosomes and the septet formula DDDD: this form belongs to the sub-species cinnamomea L. (1759) and was found by the author in 1925 in the garden of the late Canon Carew-Hunt at Albury near Oxford under the name of R. cinnamomea. The fifth tetraploid variety is a garden form of the wild diploid species EE, R. macrophylla Lindl. (em.) having the specific characters of the E septet of chromosomes and the septet formula EEEE: this form belongs to the typical R. macrophylla Lindl. and according to Regel (1877) was found in gardens at Khiva by Korolkowi: there is a plant of this at Kew named R. macrophylla var Korolkowi and another at Cambridge (from Albury) and my material has been obtained from both these plants.

These 5 tetraploid varieties have 28 somatic chromosomes (4 septets) and 14 gametic chromosomes (2 septets). In diakinesis the chromosomes are usually quadrivalent. All produce fruits freely with many fertile seeds from which plants have been raised. The seedlings examined vary varietally, have the same chromosome as the parents and are themselves regular in gametogenesis and fertile. A marked feature of 4 of these duplicated tetraploid varieties is the increased size of all their parts as compared with the diploid wild species. This appears to be due to the larger cells developed in these varieties as in the similar cases previously found in Oenothera by de Vries (1901), Gates (1909) and others in Datura by Blakeslee (1920)

b) Triploid Varieties (2n=21)

16 duplicational triploid varieties have been found in the genus and no doubt many more could easily be found by examining the numerous garden forms of the China and Tea Roses, since so far only a few of these have been examined cytologically. All the duplicational triploids found are garden varieties of the wild diploid species AA (R. sempervirens L. (em.)) having the specific characters of the A septet of chromosomes and the septet formula AAA: 11 of these belong to the group of semperflorens (Curtis), which with 4 others belong to the subspecies chinensis (Jacq.) and 1 to the group of odorata (Sweet). The semperflorens group are descended from a plant introduced from China into England in 1791 which was described and figured by Curtis (1794) and is identical with some of the Crimson China forms in gardens to-day which are triploid in their chromosome number; I have observed a case of this triploid throwing out a septet of chromosomes in a somatic cell (Hurst, 1925, f. 171).

These triploid varieties are still cultivated in China judging by Wilson's specimen No. 3611 collected in a garden in Western Hu-peh and may have arisen in cultivation centuries ago from a duplicated gamete AA arising in a diploid AA or from a cross between diploid AA and tetraploid AAAA or from a bud sport derived from a somatic cell of a tetraploid AAAA that had lost a septet of chromosomes. Among my material from Paris there is a climbing China Rose with single red flowers which closely resembles the spontaneous specimen of the sub-species chinensis (Jacq.) collected by Henry in Western Hu-peh (No. 1151) in his expedition of 1885-1888, and which is a diploid form AA with 14 somatic and 7 gametic chromosomes.

Twelve other garden forms of the subspecies chinensis Jacq. examined prove to be diploids including the original plant of the old "Blush China" introduced from China about 1789.

Polyploid varieties must be carefully distinguished from polyploid species in which the septets of chromosomes are differential and in which the chromosomes are either bivalent or bivalent and univalent in synapsis.

2. Differential Polyploid Species

In Rosa all the wild polyploids examined are differential polyploid species. Taxonomic analyses reveal and genetical experiments demonstrate that these wild polyploid species are composed of various combinations of the characters of the A, B, C, D, and E septets of chromosomes, so that one species differs from another by the presence or absence of one or more differential septets of chromosomes.

At least two distinct types of differential polyploid species may be recognized: —

a) Regular Septet species with differential septets whose chromosomes are bivalent in the synaptic stages of gametogenesis.

b) Irregular Septet species with differential septets whose chromosomes are partly bivalent and partly univalent in synapsis.

a) Regular Septet Species

Regular septet species with differential septets and bivalent chromosomes differ from one another by two or more septets of chromosomes. Since there are 5 differential septets A, B, C, D and E, 26 regular septet species are possible, vix. 10 tetraploids, 10 hexaploids, 5 octaploids and 1 decaploid. Of these 18 have been identified, viz. 9 tetraploids, 7 hexaploids and 2 octoploids. [CybeRose note: Others have since been identified.]

All these species have bivalent chromosome, their gametogenesis is regular and balanced, their reduction divisions are normal and their male and female gametes carry equal numbers of chromosome septets. All are fully fertile under normal conditions and in a wild state at all events show no signs of apomixis. These regular polyploid species are distributed in the arctic and temperate regions of the northern hemisphere, and the most polyploid species (octoploid) are circumpolar, in their distribution, so far as they are definitely known.

(i) Regular Tetraploid Species (n=14m, 14f)

AABB species (Rosa Huntii sp. nov.)

The AABB species is represented by a new species from China as yet undescribed. This was received by the late Canon Carew-Hunt from a missionary in China but its precise habitat is unfortunately unknown. The plant, now in the Cambridge Collection, is tetraploid with 4 septets (AABB) of somatic chromosomes and 2 septets (AB) of gametic chromosomes and well combines the characters peculiar to the A and B septets of chromosomes. The A septet characters are recurved stems, elongated sinuous branches, stout uniform prickles, narrow convex stipules, compound 1-20 fl. inflorescence, numerous bracts, broad disc, sub-elongated exserted styles with conical-tiered stigmas. The B septet characters are inclined and rigid stems, shortnoded and right angled branches, alate prickles, paired infrastipular above, tufted axillary leaves, narrow based stipules, flowers wreathed on short laterals, ovate-elliptical bracts, thin disc, few loose and sub-contorted styles, sepals shorter than the petals which have a sub-foetid scent. The species will be described more fully later with figures under the name of Rosa Huntii. [Rosa Huntii Hurst (sp. nov.) Rami sinuosi aculeis alatis dilatatis supra geminatis. Flores parvi (1-10) in corymbis parvis congestis serti, bracteis numerosis. Styli pauci laxi contortuli apicibus conicis concretis.]

AACC Species (Rosa centifolia L.)

The AACC species is represented by numerous forms some of which are entitled to rank as sub-species. The oldest legitimate name for this species is Rosa centifolia L. (1753): other names of the numerous sub-species and varieties examined include R. damascena Blackw. (1757), R. rubra Blackw. (1757), R. gallica L. (1759 non L. 1753), R. muscosa Mill. (1768), R. provincialis Mill. (1768), R. pumila Jacq. (1774), R. parvifolia Ehr. (1791), and R. pomponia D. C. (1805).

Sixty varieties of the type and its sub-species have been examined and all are differential tetraploids with 4 septets (AACC) of somatic chromosomes and 2 septets (AC) of gametic chromosomes. All combine the characters peculiar to the A and C septets in various ways causing much variation. Many of the varieties are cultivated forms with double or semi-double flowers but the single flowered wild forms are found in France, Central and South East Europe, Asia Minor to the Western Caucasus and Syria. The typical form was cultivated at the time of Theophrastus about 350 BC and was known to him by the same name Rosa centifolia, it is still cultivated for its petals which are made into Rose Water in France, Bulgaria, Persia and India.

So far no forms of this species have been reported from Eastern Asia or North America, except a curious variety of the Moss Rose said to be from Japan which is tetraploid and bears the combined characters of the sub-species gallica and muscosa and which is probably of garden origin. According to Rydberg (1918) gallica is sparingly naturalized in Eastern North America and Mexico.

AADD Species (Rosa palustris Marsh.)

The AADD species is represented by forms confined to Eastern North America, including Rosa palustris Marsh. (1785), R. humilis grandiflora Baker (1911 non Marsh. 1785), R. carolina L. (1762 p.p. non L. 1753), R. corymbosa Ehr. (1789) and R. Hudsoniana Thory (1817).

This species is a differential tetraploid with 4 septets (AADD) of somatic chromosomes and 2 septets (AD) of gametic chromosomes and combines the characters peculiar to the A and D septets. It is distributed from Minnesota and Mississippi to Florida and Nova Scotia in North America and has been frequently confused with R. humilis Marsh. (1785) and R. carolina L. (1753).

AAEE Species (Rosa Davidi Crép.)

The AAEE species is represented by several interesting forms recently found in Central China including R. Davidi Crép. (1874), R. setipoda Hemsl. et Wils. (1906 p.p.), R. roseo-moyesii Almq. (1922), R. macrophylla Fargesii Hort. and R. macrophylla crasseaculeata Vilm. (1903). These are differential tetraploids with 4 septets (AAEE) of somatic chromosomes and 2 septets (AE) of gametic chromosomes and combine the characters peculiar to the A and E septets in various ways causing considerable variation.

It is distributed from Western Sze-chwan to North Western Hu-Peh in China.

BBCC Species (Rosa spinosissima L. 1762)

The BBCC species is represented by Rosa spinosissima L. (1762) (also p.p. L. 1745, 1753, 1755), R. scotica Mill. (1768), R. myriacantha D. C. (1805), R. Ripartii Desegl. (1861) and R. hispida Sims (1813) (non Poiret). A new form from China received at Kew under the name of R. Chusi Mala apparently belongs to this species.

These are differential tetraploids with 4 septets (BBCC) of somatic chromosomes and 2 septets (BC) of gametic chromosomes and combine the characters peculiar to the B and C septets. It is distributed principally on the sand dunes of the coasts of Western Europe, but its eastern limits have not yet been clearly defined owing to its confusion with the following species BBDD by collectors and authors.

In both species the B septet characters are more patent and the chief distinction is in the habit of growth which in BBCC is dense and bushy with numerous tortuous branchlets while BBDD is usually erect with few acute angled virgate branchlets. From this it will be seen that the difference between R. spinosissima (BBCC) and R. pimpinellifolia (BBDD) which has been much discussed by systematists since the time of Linnaeus seems now to be on the way to solution with the aid of experimental genetics. Evidently it is not a simple difference between glandular and eglandular pedicels as was formerly supposed since either species may be glandular or eglandular, though it may be the difference between aciculate pedicels (C septet) and non-aciculate pedicels (D septet) among several other fundamental differences in habit of growth and habitat. Those who have seen R. spinosissima (BBCC) growing wild on the sand dunes of the coasts of England and France and R. pimpinellifolia (BBDD) on the rocks of the Jura Mountains in Switzerland will appreciate the true distinction between these two species.

Under the name of Scotch Rose R. spinosissima L. has been cultivated for many years and it was well known to botanists in the 16th century. Unfortunately its botanical history is much intermixed with the following species, which has BBDD chromosomes and characters with a distinct habit of growth, a different habitat and apparently a more general distribution.

BBDD Species (Rosa pimpinellifolia L. 1759)

The BBDD species is represented by numerous forms and distinct sub-species, e.g. Rosa pimpinellifolia L. (1759) (1762) also p.p. (1771), R. foetida Herrm. (1762), R. hemispherica Herrm. (1762), R. lutea Mill. (1768), R. punicea Mill. (1768), R. altaica Willd. (1809), R. lutescens Pursh. (1814), R. ochroleuca Swartz (1820), R. grandiflora Lindl. (1820), and R. Rapini Boiss. and Bal. (1859). These are all differential tetraploids with 4 septets (BBDD) of somatic chromosomes and 2 septets (BD) of gametic chromosomes and combine the characters peculiar to the B and D septets in various ways causing much variation. [1932 note: R. fedtschenkoana Regel.]

This species has a wide distribution in Europe and Asia extending from Wales, Eastern France and Switzerland to the Caucasus, Persia, Turkestan, Mongolia and possibly Manchuria and Northern China: from certain specimens I have examined collected by Hooker and Thompson in the Himalaya there is little doubt that this species also extends south to India. So far I have not been able to trace it as spontaneous in North America.

30 sub-species and varieties of this species have been studied cytologically and various crosses and genetical hybrids have been raised at Burbage and Cambridge.

BBEE Species (Rosa multibracteata Hemsl. et Wils.)

The BBEE species is represented so far by a few forms confined to Central and North China though there is a living specimen at Kew labelled "R. Webbiana, Himalaya" which belongs to this species. The oldest form is Rosa multibracteata Hemsl. et Wils. (1906) from Western Sze-chwan, China (including R. reducta Baker [1914]) and the most recent form is R. bella Redd. et Wils. (1915) from North West Shan-si, China. These are differential tetraploids with 4 septets (BBEE) of somatic chromosomes and 2 septets (BE) of gametic chromosomes and combine the characters peculiar to the B and E septets.

CCDD Species (Rosa virginiana Mill.)

The CCDD species is represented by numerous forms the oldest of which is R. virginiana Mill. (1768) known to botanists until recently under the name R. lucida Ehr. (1789), others are R. baltica Roth. (1789), R. suffulta Greene (1899), R. Lunellii Greene (1911), R. saturata Lamm., and several new sub-species and varieties raised at Burbage from seeds received from North America where the species has wide distribution. The form baltica is apparently naturalised on the German shores of the Baltic, at the mouth of the Elbe and on the Western coast of France at the mouth of the Loire and differs in minor characters from the type. R. saturata is a subspecies found at Kew, and said to be from China, which closely resembles R. johannensis Fern. (1918) from New Brunswick and Maine USA.

These are all differential tetraploids with 4 septets (CCDD) of somatic chromosomes and 2 septets (CD) of gametic chromosomes and combine the characters peculiar to the C and D septets in various ways.

The type of the species is distributed on the eastern coast of North America from Alabama to Newfoundland, while the American sub-species range from Alberta to Manitoba in Canada and from North Dakota to Texas and Illinois in the United States.

CCEE Species (missing)

The CCEE species has not yet been identified in a wild state though the genetical diploid hybrid Rosa macrophylla x rugosa, which represents a combination of E septet maternal characters with C septet paternal characters, indicates the CE septet characters that may be looked for in the missing wild tetraploid species CCEE.

DDEE Species (Rosa pendulina L.)

The DDEE species is represented by numerous forms several of which are entitled to rank as sub-species. The oldest legitimate names for this species are Rosa cinnamomea L. (1753) (non R. cinnamomea L. 1759, 1762 et auct.) and R. pendulina L. (1753). The latter name is now coming into use for this species in preference to the name R. alpina L (1762) which has been generally used by botanists for more than a century. Other forms and sub-species are R. monspeliaca Gouan (1765), R. inermis Mill. (1768), R. pyrenaica Gouan (1773), R. lagenaria Vill. (1789), R. glandulosa Bellardi (1790), R. laxa Retz. (1803) (non Lindl. 1820), R. oxyodon Boiss. (1872), R. intercalaris Desegl. (1873), R. adjecta Desegl. (1873), R. Bordereana Rouy. (1900) and R. acicularis nipponensis auct. (non R. nipponensis Crép. (1875). 40 varieties of the type and its sub-species have been examined cytologically and taxonomically and 20 of these were collected personally in the Alps of Switzerland, 7 were found in the Lower Engadine, 6 in Canton Ticino, 3 in Canton Uri, 3 in Canton Schwyz and 1 in the Upper Engadine. All these forms are differential tetraploids with 4 septets (DDEE) of somatic chromosomes and 2 septets (DE) of gametic chromosomes. All combine the characters peculiar to the D and E septets in various ways leading to much variation.

This species has a wide distribution in the Alpine regions of Europe from the Pyrenees to the Carpathians and Greece. In Asia it extends to the Caucasus, Turkestan and Mongolia but I have not yet been able to identify it positively in either China or North America, though I suspect that the tetraploid forms of so called "R. blanda" belong here. In Switzerland I found this species growing in a peculiar habitat from about 1,000 to 2,000 metres above sea level and never found it at lower or higher elevations.

(ii) Regular Hexaploid Species (n=21m, 21f)

Regular hexaploid species are comparatively rare in my material since out of 674 individuals examined only 19 are regular hexaploids. Täckholm (1922) found 11 regular hexaploids out of 293 individuals examined; Blackburn and Harrison (1924) found 1 out of 30 and Penland (1923) 2 out of 9, so that out of a total of 1006 Roses examined only 33 were regular hexaploids.

On the basis of the 5 differential septets in Rosa 10 differential regular hexaploid species are possible and 7 of these have been identified as shown below, leaving 3 species still to be found (if they exist).

AABBCC = Rosa Wilsoni Borr. (1830), N. Wales, N. Ireland, Scotland.
AABBDD = Rosa manca Greene. (1890), Rocky Mountains of North America.
AABBEE = Rosa Moyesii Hemsl. et Wils. (1906) S.W. and Central China from Yun-nan to W. Sze-chwan and Kan-su at 2000-3600 metres altitude.
AACCDD (missing)
AACCEE (missing) [1932 note: R. hemsleyana Täckh.]
AADDEE = Rosa nutkana Presl (1851), N. America from Alaska to British Columbia, Wyoming and Oregon.
BBCCDD = Rosa Bourgeauiana Crép. (1876) N. America, Mackenzie, Montana, Colorado to Ontario and Hudson Bay.
BBCCEE (missing)
BBDDEE = Rosa Engelmanni S. Wats. (1889), N. America, Rocky Mountains, N. Dakota and S. Montana to Colorado.
CCDDEE = Rosa Sayi Schwein. (1824) N. America

(iii) Regular Octoploid Species (n=28m, 28f)

Octoploid species are very rare in my material since out of 674 individuals examined only 5 are octoploids. Täckholm (1922) found 3 octoploids out of 293 individuals examined while Blackburn and Harrison (1921) and Penland (1923) found none out of 39 examined: so that out of a total of 1006 Roses examined only 8 were octoploids. On the basis of the 5 differential septets in Rosa 5 differential regular octoploid species are possible and 2 of these have been identified leaving 3 species still to be found (if they exist), as shown below:—

AABBCCDD = Rosa Täckholmii sp nov.* No. 190 Täckholm (1922) = R. hibernica Hook (1813). (non Templ. (1803) nec Sm. 1810) Iceland.
AABBCCEE (missing)
AABBDDEE (missing)
AACCDDEE (missing) [1932 note: R. acicularis Hort. Kew (R. acicularis Lindl. p.p. cum icon)]
BBCCDDEE = Rosa acicularis Lindl. (1820) [1932 note: R. baicalensis, Turcz.] Arctic and subarctic Europe, Asia and America, circumpolar

[* Rosa Täckholmii Hurst (sp nov.) Rami elongati aculeis inaequalibus infra confertis aciculis setis glandulosis supra geminatis longis dilatatis alatis. Stipulae longae angustae. Flores solitarii V. pauci. Styli breves tomentosi. Fructus urceolatus sepalis erectis coronatis, serotinus.]

b) Irregular Septet Species

The irregular septet species with differential septets have both bivalent and univalent chromosomes so that in synapsis some of the chromosomes are paired and balanced while others are unpaired and unbalanced.

These species differ from one another by 1 or more septets and out of 180 different combinations possible on the basis of the various combinations of the 5 differential septets A, B, C, D and E with a paired septet only 25 have been so far identified in a wild state and 6 of these are evidently natural hybrids growing near the putative parents.

Three of the septet combinations have been made genetically thus demonstrating experimentally the possible hybrid origin of these species.

Three distinct features are peculiar to these irregular species:—

1. These species are confined in their distributions to the Old World in temperate Europe and Western Asia in an area more or less conterminous with that of the Pleistocene Ice Sheet at its maximum southern and eastern limits of influence.

2. These species, so far as they have been tested genetically, (12) appear to be facultatively apomictical with irregular but partly fertile pollen. (It is difficult to distiguish apomictical from homozygous seedlings in a state of nature.)

3. All these species present the phenomenon, at present unique in plants and animals, of a regular but unequal reduction division in female gametogenesis which causes them to produce female gametes carrying from 2 to 5 times as many septets as their male gemetes, so that their reciprocal hybrids ae entirely different in their chromosome content and in their characters (see Hurst (1925) f. 172) and Expts. 23-28 below.

All are fully fertile producing apomictical or sexual seeds in abundance and they maintain themselves so well in ordinary conditions as to dominate the rose population in Europe, e.g. the species of the section Caninae commonly known as "Briars" all belong to the irregular septet species of Rosa.

The irregular septet species of Rosa are either tetraploids with 4 septets, pentaploids with 5 septets or hexaploids with 6 septets of somatic chromosomes; no triploids with 3 septets, have yet been found in a wild state. It is remarkable that all the 19 irregular septet species whether tetraploid, pentaploid or hexaploid carry in their male gametes only 1 septet of chromosomes, while in their female gametes the tetraploids carry 3 septets, the pentaploids 4 septets and the hexaploids 5 septets of chromosomes. A few wild forms carry 2 septets of chromosomes in their male gametes, when they are fertile, but all these that I have examined appear to be natural hybrids growing with their putative parents. Many of thest phenhybrids are more or less sterile, in their pollen at all events, and produce few seeds either sexually or apomictically. Genetical experiments however demonstrate that some of these natural hybrids are partially fertile especially when used as the mother parent.

The following is a list of the 19 irregular septet species so far identified as wild species together with the formulae of their septet characters, the septet constitution of their male and female gametes and their distribution in Europe and Asia. Each species has numerous sub-species and varieties all of which come under the oldest binomial name which is the only one noted here. Further research will no doubt lead to the discovery of older names for some of these species.

It will be recognised that the septet characters of the higher polyploid irregular septet species are difficult to analyse since in the pentaploids the single septets present only about one fifth of their total characters while the hexaploids show only about one fifth of their total characters while the hexaploids show only about one sixth of their total charactrers owing to the various interactions of the other septets. On the other hand the tetraploids are more easy to analyse as they show about one fourth of their total characters in the single septets. In view of these difficulties it is possible that further research may modify some of the septet formulae presented below although in the main there is no doubt that they are correct since many of them have been tested genetically and experimentally.

[CybeRose note: I have shortened the following table by eliminating redundant phrasing in all but the entry for R. omissa, which may serve as model for the rest. In each case the double septet is paired, one going alone to the pollen while the other remains with the unpaired septets in the ova.]

(i) Irregular Tetraploid Species

(1 septet in male gametes, 3 septets in female gametes)

Rosa omissa Desegl. (1864 p.p.) (AACD) This species combines the A, C and D septet characters approximately in the ratio of 2A:1C:1D: this analysis is based on material sent me by Dr. Heslop Harrison from Co. Durham. This sub-Alpine species is distributed in Western and Central Europe and Scandinavia.

R. recondita Puget (1866) (CCDE) based on material collected by the author in the Alps of Switzerland. This Alpine species ranges from the Pyrenees to the Caucasus.

R. mollis Smith (1812) (CDDE) based on material collected by the author in England and Switzerland. This Alpine and sub-Alpine species is distributed over Europe.

R. pomifera Herrm. (1762 p.p.) (CDEE) based on material collected in Switzerland and in the species collections at Burbage and Cambridge. This species is both sub-Alpine and Alpine and is distributed from the Pyrenees to the Caucasus and in Scandinavia.

R. rubrifolia Vill. (1789) (ADDE) based on material collected in the Alps of Switzerland and in the species collections at Burbage and Cambridge. This purely Alpine species is distributed in Europe from the Pyrenees to Montenegro.

(ii) Pentaploid Species

(1 septet in male gametes, 4 in female gametes)

R. agrestis Savi (1798) (AABCD) based on material collected by the author in England: it is distributed over Western, Central and Southern Europe and naturalised in North Africa.

R. canina L. (1753) (em.) (AABDE) This species includes a majority of the forms of the sub-section Eu-caninae Crép. Based on material collected by the author in England: the species is widely distributed in the lowlands of Europe and West Asia and naturalised in North Africa and all parts.

R. micrantha Smith (1812) (AABCE) based on material collected by the author in England: the species is distributed over Western, Central and Southern Europe, Armenia and the Caucasus and naturalised in N. Africa and N. America.

R. tomentosa Smith (1800) (AACDE) based on material collected by the author in England: the species is distributed in Western, Central and South Eastern Europe, Armenia and the Caucasus.

R. rubiginosa L. (1771) (ABBCD) based on material collected by the author in Midland and Eastern England: the species is distributed in Western, Central and Southern Europe and naturalised in various parts of the world.

R. elliptica Tausch (s.s.) (ABBCE) based on material collected by the author in Switzerland and also on plants raised from seeds collected in North America where it has become naturalised: the species is apparently confined to Central Europe and Continental Italy, though its Eastern Limits are not yet well defined.

R. glutinosa Sibth. and Sm. (1806) (BCCDE) based on material in the Kew collection: the species is distributed from maritime Italy to Armenia and the Taurus, though its eastern limits are not yet clearly defined as many specimens labeled R. glutinosa really belong to R. sicula Tratt. or to R. ferox Bieb. and these extend into the Caucasus and Persia.

R. pseudo-mollis Ley. (1907) (ABCDD) based on material collected by the author in Eastern England; this may be a natural hybrid from R. Eglanteria x mollis with which it grows.

R. coriifolia Fries. (1814) (ACDDE) based on material collected by the author in Switzerland: this Alpine species is distributed in Western Europe and Scandinavia and from the Pyrenees to the Caucasus.

R. glauca Vill. (1809) (ABDDE) based on material collected by the author in the Alps of Switzerland: this Alpine species is distributed in Western Europe, Scandinavia and from the Pyrenees to the Caucasus.

R. Froebeli Christ. (1903) (ACDEE) based on material used in nurseries as a stock for budding Roses and known as Rosa laxa Hort. (non Retzius nec Lindl.) which was originally received at Zurich from Asia Minor. In the British Museum I have seen many specimens of this species collected in 1892-93 by Bornmüller in Kurdistan (see B.M. Spec. No. 1051 in packet B.M. 75).

(iii) Irregular Hexaploid Species

(1 septet in male gametes, 5 septets in female gametes)

R. Pouzini Tratt. (1823) (et auct.) (AABCDE) based on material in the Kew collection of a form found in the County of Surrey, England, and named by Wolley-Dod (1924) R. canina var. Pouzini f. simplicidens. The species is distributed in Western and Southern Europe from Portugal to Greece.

R. inodora Fries (1814) (non Borrer nec Hooker) (ABBCDE) based on Täckholm's (1922) material at Uppsala: it is distributed in Western Europe and Scandinavia but its eastern and southern limits are not yet definitely defined owing to its confusion with R. elliptica Tausch and R. agrestis Savi.

R. Jundzilli Bess. (1816) (ABCCDE) based on material in the Kew collection and also on Täckholm's (1922) ample material in Sweden and Denmark: the species is distributed in Central and South Eastern Europe, Armenia and the Caucasus.

Experimental Proofs

In addition to the cytological and taxonomic observations detailed above, the following genetical tests have been made. Roses being woody shrubs are naturally slow genetical material the normal time for a generation in some species being about 6-8 years and the most rapid being about 3 years, so that the technical difficulties of raising several generations are considerable. (Fortunately only F1 tests are required for testing out Septet chromosomes and characters.) The genetical slowness of Rosa material is however fully compensated by its permanence, for the individual plant is able to live to an extreme age e.g. the well-known Rose (R. canina L.) growing on the cathedral at Hildesheim, in Germany according to documentary evidence was in existence at the time of Lous-le-Débonnaire in A.D. 818, and further its life be indefinitely prolonged by vegetative propagation.

1. AA x AA = AA. 7 sub-species viz. arvensis (Huds.), chinensis (Jacq.), moschata (Herrm.), multiflora (Thunb), sempervirens (L), Wichuraiana (Crép.) and rubifolia (R. Br.) have been crossed inter se and are fully fertile, in several cases F2 generations have been raised. Thousands of selfed seedlings of multiflora, Wichuraiana and rubifolia have been raised at Burbage and all bred true to the A septet specific characters, and also to their own sub-specific characters with considerable Mendelian seregation in their varietal characters.

2. BB x BB = BB. Crosses have been raised between sericea (Lindl.) x Hugonis (Hemsl.) and x omeiensis (Rolfe) at Cambridge which are fully fertile yielding F2 generations. It is interesting to note here that Endlicher (1836-1840), Crépin (1872) and later authors have placed sericea (Lindl.) in a separate Section of the genus, mainly on account of its tetramerous flowers. My observations show that pentamerous flowers frequently occur in both sericea and omeiensis, indeed in one instance a tetramerous bush of the former at Cambridge after a severe pruning was almost entirely pentamerous in the following year. Hundreds of selfed seedlings of 7 varieties of sericea and omeiensis have been raised at Burbage and Cambridge and all bred true to the B septet characters.

3. CC x CC = CC. Hundreds of seedlings of Rosa rugosa Thunb. (em.) have been raised at Burbage and Cambridge, including seedlings of the sub-species rugosa (Thunb.) from seeds collected in Japan, selfed seedlings of nipponensis (Crép.) and seedlings of nitida (Willd.) from seeds collected in North America and all bred true to the C septet characters.

4. DD x DD = DD. Hundreds of seedlings of Rosa carolina L. (1753) (em.) have been raised at Burbage including the sub-species blanda (Ait.) from seeds collected in North America and all breed true to the D septet characters.

5. EE x EE = EE. A few selfed seedlings of Rosa macrophylla Lindl. (em.) have been raised at Burbage and bred true to the E septet characters.

In all the above cases the 5 diploid species have bred true to their A, B, C, D and E specific and diagnostic characters. In all cases too their sub-species have bred true to their sub-specific major alternative characters.

In some cases their varieties and forms have bred true to their minor alternative characters while in others Mendelian segregation has taken place the varieties and forms being heterozygous in certain characters, extracted forms breeding true.

6. AA x CC = AC. R. multiflora (AA) x R. rugosa (CC) has given several F1 sterile differential diploid hybrids (AC) all of which bear the combined characters of the A and C septets of chromosomes.

7. CC x AA = AC. Reciprocal crosses give similar results e.g. R. rugosa (CC) crossed with R. multiflora (AA), arvensis (AA) and odorata (AA) all gave F1 sterile differential diploid hybrids AC which have the combined characters of the A and C septets of chromosomes. These diploid hybrids AC resemble in their characters the tetraploid wild species AACC (R. centifolia L.) and experimentally demonstrate the differential nature of this polyploid species. Some interesting differences have been observed in the way the A and C septet characters manifest themselves in the diploid hybrids with a single septet of A and C and in the tetraploid species AACC with a double septet of A and C and these will be dealt with in detail in a forthcoming book. [CybeRose note: Sadly the book was not published so far as I can find.]

8. DD x AA = AD. Hybrids between the diploid species R. cinnamomea (DD) and chinensis (AA) and between californica (DD) and multiflora (AA) are all sterile differential diploids AD which have the combined characters of the A and D septets of chromosomes. These diploid hybrids AD resemble in their characters the tetraploid wild species AADD (R. palustris Marsh.) and demonstrate the differential nature of this polyploid species.

[CybeRose note: This is more than a little confusing: Erlanson found R. californica C. & S. to be tetraploid though Täckholm found it diploid. The carolina-palustris confusion finally got settled out (no thanks to Linneaus) with R. palustris Marsh. (R. carolina L. 1762 non 1753) joining DD, and R. carolina L. 1753 (R. humilis Marsh.) taking its place with the AADD.]

9. DD x CC = CD. R. foliolosa (DD) and R. rugosa (CC) and between R. cinnamomea (DD) and R. rugosa (CC) are all differential diploids CD which combine the characters of the C and D septets.

10. CC x DD = CD. The reciprocal hybrid R. rugosa (CC) x R. blanda (DD) gave a similar result and all these diploid hybrids CD resemble in their characters the tetraploid wild species CCDD (R. virginiana Mill.) and experimentally demonstrate the differential nature of this polyploid species.

11. EE x CC = CE. The F1 hybrid between the diploid species R. macrophylla (EE) and R. rugosa (CC) is a differential diploid CE which combines the characters of the C and E septets of chromosomes and demonstrates genetically and experimentally the characters of the missing tetraploid species CCEE which may exist in a wild state but has not yet been identified.

12. AADD x CC = ACD. R. palustris (AADD) x R. rugosa (CC) is a differential sterile triploid ACD which combines the characters of the A, C and D septets of chromosomes and demonstrates genetically and experimentally the characters of the missing species AACCDD which may exist in a wild state but has not yet been identified.

13. AA x AACC = AAC. R. chinensis (AA) x R. gallica (AACC) and x damascena (AACC), R. Wichuraiana (AA) x R. centifolia (AACC), R. multiflora (AA) x R. gallica (AACC), the diploid cross (R. multiflora x chinensis) (AA) x R. gallica (AACC), the same diploid cross (AA) crossed with the tetraploid cross (R. centifolia x gallica) (AACC), all produced differential triploid hybrids (AAC) which combine the characters of the A and C septets of chromosomes approximately in the ratio of 2A:1C.

14. CC x AAAA = AAC. A similar result was obtained by crossing the diploid species R. rugosa (CC) with a tetraploid variety of the diploid species AA: this tetraploid was itself (AAAA) derived from secondary grosses between the diploids chinensis, moschata and odorata and has in some way duplicated its A septets of chromosomes under cultivation. [CybeRose note: this tetraploid may have been Gloire de Dijon.]

15. AACC x CC = ACC. R. gallica (AACC) x R. rugosa (CC) gave ACC.

16. CC x AACC = ACC. The reciprocal cross of (15) above gave a similar result.

17. BB x BBCC = BBC. R. Hugonis (BB) x R. spinosissima (BBCC) gave BBC.

18. CC x BBCC = BCC. R. rugosa (CC) x R. spinosissima (BBCC) gave BCC.

19. BB x BBDD = BBD. R. Hugonis (BB) x R. altaica (BBDD) gave BBD.

20. CCDD x DD = CDD. R. lucida (CCDD x R. Woodsii (DD) gave CDD.

21. BBCC x BBDD = BBCD. R. spinosissima (BBCC) x R. lutea (BBDD) produced the differential hybrid BBCD. 2B:1C:1D.

22. BBCC x AACC = ABCC. R. spinosissima (BBCC) x R. damascena (AACC) produced the differential hybrid ABCC. 1A:1B:2C.

23. CC x ABBCD = BC. The diploid species R. rugosa (CC) crosed with the pentaploid species R. rubiginosa (ABBCD — male gametes B) produced the differential diploid hybrid BC which combines the characters of the B and C septets of chromosomes approximately in the ratio 1B:1C with no trace of the characters of the paternal septets A and D. This genetical experiment demonstrates that the male gametes of the irregular pentaploid species R. rubiginosa (ABBCD) carry only 1 septet of chromosomes, and that the septet is the reduced bivalent B. From other experimental evidence (see Nos. 26, 27 and 25) we know that the female gametes of the same plant carry 4 septets of chromosomes viz: ABCD.

24. CC x AABDE = AC. R. rugosa (CC) x R. canina (AABDE) gave a differential diploid AC. This demonstrates that the male gametes of R. canina (AABDE) carry only 1 septet of chromosomes and that septet is the reduced bivalent A (cf. also No. 28)

25. ABBCD x AA = AABCD. R. rubiginosa (ABBCD) x R. chinensis (AA) gave AABCD. This demonstrates that the female gametes of R. rubiginosa (ABBCD) carry 4 septets ABCD. (Cf. Nos. 26 and 27)

26. ABBCD x AACC = AABCCD. R. rubiginosa (ABBCD) x R. damascena (AACC) gave AABCCD. This again demonstrates that the female gametes of R. rubiginosa (ABBCD) carry 4 septets ABCD (cf. Nos. 25 and 27).

27. ABBCD x BBDD = ABBCDD. R. rubiginosa (ABBCD) x R. lutea (BBDD) gave ABBCDD. This demonstrates for the third time that the female gametes of R. rubiginosa carry 4 septets ABCD (cf. Nos. 25 and 26).

28. AACCDE x AABDE = AACDE. xR. alba (AACCDE) x R. canina (AABDE) gave AACDE. This demonstrates two important facts (a) that the female gametes of xR. alba (AACCDE) carry 4 septets ACDE while (b) the male gametes of R. canina (AABDE) carry only A.

29. CC x BBCCDDEE = BCCDE. R. rugosa (CC) x R. acicularis (BBCCDDEE) gave BCCDE.

Other Genera of the Tribe Roseae

Among the 377 diploid Roses examined are 4 very distinct species Rosa Persica Michx. (1789), R. microphylla Roxb. (1820), R. bracteata Wendl. (1798) and R. minutifolia Engelm. (1882). Each of these species has 1 septet of gametic chromosomes and 2 septets of somatic chromosomes but the septet characters of these 4 species do not correspond with any of the 5 septets of Rosa. These 4 diploid species are so distinct from the ordinary species of Rosa that almost all authors have placed them in 4 isolated sections, many have classed them as subgenera while several have ranked them as distinct genera which my researches confirm.

1. R. persica Michx. was raised to generic rank by Du Mortier (1824) under the name of Hulthemia, by Ledebour (1830) under the generic name of Rhodopsis and by Lindley (1829) under the generic name of Lowea. Hulthemia is distinguished from Rosa by its simple leaves, absence of stipules, stomata on both sides of the leaflets, inwardly dehiscent anthers, yellow petals with large crimson basal area and densely prickly fruits. It is a monotypic genus widely scattered over (but confined to) the deserts of Central Asia (H. persica).

2. R. microphylla Roxb. was raised to generic rank by Decaisne (1850) under the name of Platyrhodon and is distinguished from Rosa by its spiny or thorny prickles, its cup-shaped (not urceolate) receptacle covered with large fleshy spines and with wide apex and disc, within which is a central memelon reminding one of the torus of Rubus but enclosed like Rosa and almost forming a two-chambered receptacle: it is also distinguished by its deciduous bark like Platanus and its 11-15 foliolate leaves.

Platyrhodon is a monotypic genus distributed in South West and Central China and Japan (P. microphylla) [CybeRose note. R. roxburghii]

3. R. bracteata Wendl. was raised to generic rank by Germain de Saint Pierre (1878) under the name of Ernestella and is distinguished from Rosa by its recurved and deflexed spiny prickles, tomentose inflorescence and fruits and copious imbricate, incised, involucrate bracts, large disc and flowers with innumerable stamens and carpels. Ernestella is a monotypic genus the type of which is found in South East China (E. bracteata) with a single sub-species involucrata (Roxb. 1820) [CybeRose note: R. clinophylla] which is widespread over the hot moist plains and lower mountains of India and Burma though confined to certain habitats often far apart.

4. R. minutifolia Engelm. was raised to generic (or sub-generic) rank by Cockerell (1913) under the name of Hesperhodos and is distinguished from Rosa by its few, small, incised, cuneate-truncate leaflets reminding one of certain species of Ribes and Potentilla, short stipules, densely prickly fruits and sepals, the sepals are compound lobed and foliaceous below reminding one of certain species of Fragraria. Hesperhodos is a monotypic genus with 2 sub-species, the type H. minutifolia is confined to Lower California, the sub-species stellata (Wooton 1898) is distributed from West Texas to Arizona and is distinguished by its stellar trichomes while the sub-species mirifica (Greene 1910) is confined to the White and Sacramento Mountains, New Mexico, according to Rydberg (1918).

The primitive nature of many of the characters of the 4 genera above suggest that these monotypic genera may be relict diploid species of the Tertiary which by their geographical position escaped the rigours of the Pleistocene Ice Age but remained diploid and primitive and have not evolved into polyploid and distinct diploid species like their sister genus Rosa.

Hurst Bibliography