Botanical Gazette, December 1934
Analytical key to the North American species of Cinnamomeae
Eileen Whitehead Erlanson

A Calyx lobes after flowering usually deciduous. Inflorescence usually glandular.
B Calyx lobes usually spreading or reflexed in fruit, and falling separately from the disc. Pedicels erect in fruit. Achenes densely hirsute. Habitat, east of 100th meridian west and north to the St. Lawrence basin.
C Shrubs of bogs and moist shores. Leaflets 7-9, narrow-oblong, acute at each end, finely serrate.
D Usually 1-2 m. tall, flowering laterals 10 cm. long or more. Inflorescence corymbose.
E
R. palustris
2n=14
Often armed with flattened infrastipular prickles. No. of teeth on each side of leaf average 26. Stamens over 200. Sepals usually reflexed on the fruit and deciduous. Late flowering.
EE
R.X schuettiana
2n=14
Almost unarmed, prickles weak. No. of teeth average 19. Stamens 150-180. Sepals usually erect and persistent or tardily deciduous. Flowering between R. blanda and R. palustris.
DD
R. nitida
2n=14
Stems low, under 1 m., usually armed with copious reddish bristles. Flowering laterals under 10 cm. long, flowers 1-3 together. Teeth fine, acute, av. no. 16.
CC Shrubs of rocky shores, dry uplands, and plains.
F
R. virginiana
2n=28
Stems stout, much branched. Suckers few, rarely flowering in first season. Leaflets firm and elliptic. Bristles at base and on new shoots, prickles flattened or absent. Teeth 9-30 (av. 14). Stamens 120-155. Newfoundland to eastern Pennsylvania. [stamens ave. 140]*
FF Stems usually slender, often bristly to tips, if stout usually simple; often decumbent or bending after first season. Prickles, if present, usually terete. Many suckers which often flower with terminal corymbs after main flowering period. Highly variable and "weedy" species.
G
R. carolina
2n-28
Leaflets mostly 7, highly varied in shape and texture. Teeth coarse, 5-21, av. 12. Stamens 65-130, av. 105. Hypanthium glandular of smooth.
GG Leaflets mostly 9. Hypanthium often eglandular.
H
R. X rudiuscula
2n=28
Leaflets elliptic to oval, stems bristly to top, erect and simple, or branched and decumbent. Sepals usually spreading in fruit, tardily deciduous or persistent. Stamens 65-143, av. 115.
HH
R. foliolosa
2n-14
Leaflets narrow to linear-oblong, acute, glabrous and lustrous above, coarsely serrate. Low and semi-herbaceous, stems almost unarmed. Habitat, southern Great Plains.
BB
R. gymnocarpa
2n-14
Calyx lobes falling as a group together with the disc. Inflorescence 1-3 flowers. Pedicels drooping in fruit. Stamens 55-72. Achenes few, large, glabrous. Habitat, west of Great Plains.
AA Calyx lobes usually persistent after flowering.
I Twigs, prickles, and bristles finely pubescent.
J
R. rugosa
2n=14
Stems stout, bristly, and prickly, occasionally blooming on the turions. Leaflets large, 2-4 cm., elliptic or narrow-obovate, thick, rugose above. Corymbs small. Fruit usually pendent. Foliage eglandular.
JJ
R. durandii
2n=28
Plants of Pacific Coast region of USA. Habit varied, 0.3-1.6 m., usually strict. Stems bristly, prickly, and sometimes glandular-hispid. Leaflets small (usually under 2.5 cm.), broadly oval to orbicular, often glandular-muriculate and resin-scented. Inflorescence 1-3. Infrastipular prickles alate, flattened to terete.
II Twigs, prickles, and bristles glabrous or merely glandular-hispid.
K Infrastipular prickles absent.
L Flowering on laterals from two-year or older wood only. Flowering period short, definite. Upper stipules dilated.
M Stems unarmed, bristly only at base.
N
R. williamsii
2n-14?
Inflorescence 1-2. Petals 1.7-2 cm. Sepals reflexed and persistent on the fruit. Calciphile plants. Bic, Quebec.
NN Inflorescence 1-20. Flowers subtended by ovate bracts. Sepals erect or spreading on fruit.
O
R. woodsii
2n=14
Sepals 1.5-2.5 mm. wide, 8-23 mm. long, not narrowed toward base. Leaflets oval to obovate, serrations coarse, acute ascending, av. no. 12. Petals 1-2.5 cm. long. Stamens, av. no. 65. Fruit turning red in 3-4 weeks. Habitat west of 100th meridian.
OO Sepals 2-4 mm. wide.
P
R. pisocarpa
2n=14
Small-flowered slender roses found west of Sierra Nevadas. Leaflets ovate with cordate base and fine crenate teeth (av. no. 15). Sepals 2-3 mm. wide, 8-15 mm. long, constricted toward base. Stamens, av. no. 65. Petals 10-18 mm. Fruit needing over 2 months to ripen.
PP
R. blanda
2n-14
Large-flowered eastern roses. Leaflets oval or obovate. Teeth coarse, acute, ascending (av. no. 12). Petals 2-2.8 cm. Stamens 85-140. [stamens ave. 115]*
MM Stems bristly to tips or nearly so. Leaflets 5-7 (rarely 9). Habitat, Canada and northern USA.
Q Plants 0.3-2 m. tall. Early flowering.
R
R. acicularis
2n=42 and 56
Teeth ovate. Inflorescence 1-3 on laterals less than 7 cm. long. Petals 2.5-3 cm. Stamens 65-125. Early flowering northern plants. fruits reddening in 3-4 weeks.
[ave. stamens: hexaploid 100, octoploid 75]*
RR
R. blanda var. hispida
2n-14
Teeth acute, ascending. Inflorescence 1-20 on laterals usually over 7 cm. long. Stamens 85-140. Flowers in June; fruits reddening in 5 weeks.
QQ
R. alcea
2n=28
Plants less than 3 dm. high, flowering after hexaploid and diploid species. Bristles short and weak. Flowers usually solitary. Habitat, northern Great Plains.
LL Flowering terminally in corymbs on suckers, as well as laterally on older wood. Everblooming. Flowering period extended.
R Stems unarmed, usually less than 3 dm. high.
S
R. spithamaea
2n=28?
Leaflets 5, rarely 7, usually glandular. Hypanthium usually glandular-hispid. Pacific Coast forms.
SS
R. alcea
2n=28
Leaflets 7-9, coarsely serrate. Flowers solitary or in small corymbs. Flowering on suckers rare. Habitat, northern Great Plains.
RR Stems bristly to tips.
T
R. spithamaea
2n=28?
Leaflets 5, rarely 7, usually glandular. Hypanthium usually glandular-hispid. Semi-herbaceous dwarf. Habitat, Pacific Coast.
TT
R. arkansana
2n=28
Leaflets 7-9 or 11, coarsely serrate. Teeth 7-21. Prairie forms; 0.1-1 m. high. Inflorescence 1-20, terminal or on laterals [stamens ave. 120]*
KK Infrastipular prickles usually present.
U
R. cinnamomea (introduced)
2n=14
Stipules at least on the shoots, more or less convolute. Prickles curved. Leaflets pale beneath, eglandular.
UU Stipules flat.
V Inflorescence 1-3 on short laterals (3-10 cm. long).
W Stems bristly at base only, stout with more or less flattened prickles. Foliage often glandular and resin-scented.
X
R. nutkana
2n=42
Stems over 1 m. tall, much branched, with straight ascending or recurved prickles. Petals 2.5-3 cm. Stamens 65-115. Hip 10-18 mm. in diameter. Fruit firm, needing 10 weeks or more to ripen.
XX
R. manca
2n=42
Stems low, 0.2-1 m. Prickles often recurved. Petals 1.5-2.5 cm. Hip 1 cm. in diameter. Southern Rocky Mountains region.
WW Stems bristly to top, slender or, if stout, simple and strict; height to 1 m.
Y Hips usually erect, pedicels glabrous or glandular, 0.5-2 cm. long. Pacific Coast species.
Z Stems strict, to 1.6 mm., foliage often glandular.
a
R. durandii
2n=28
Serrations fine, 9-17. Stem and pedicels often glandular-hispid. Prickles straight, flattened or terete. Leaflets usually densely puberulent and resin-scented. Petals 2 cm. long. Stamens about 70.
aa
R. californica var. bidenticulata
2n-28
Serrations coarse, 4-14; leaflets 0.5-2.5 cm. Stems with scattered weak bristles and prickles. Petals 12-18 mm.
ZZ
R. yainacensis
2n=28
Stems low to 5 dm., with strict branches and numerous weak bristles and prickles. Leaflets to 2 cm. long, oval to orbicular. Petals 1.5-2 cm. Stamens 60-70.
YY Hips usually pendent. Pedicels slender, 1-3 cm. long.
b
R. X engelmannii
2n=42
Early flowering. Petals 2.5 cm. Hips 1 cm. or more in diameter, reddening in 5-6 weeks. Stems low, with arching branches. Prickles and bristles slender. Rocky Mountain species.
bb Petals 10-25 mm. Hips less than 1 cm. in diameter. Stems slender, branched, prickles very weak. Sepals 4-5 mm. broad. Habitat, mountains of far west.
c
R. gymnocarpa
2n=14
Sepals rarely caudate, about 10 mm. long, falling together with the disc. Pedicels often glandular-hispid.
cc
R. calvaria
2n=14
Sepals caudate, about 15 mm. long, erect or spreading and persistent on the ripe fruit. Dwarf of southern Sierra Nevadas
VV Inflorescence 1-15 or more. flowering laterals usually over 10 cm.
d Sepals 1.5-2.5 mm. wide, not narrowed at base. flowers on laterals from old wood. Buds tapering. Habitat, Great Plains and westward.
e
R. woodsii
2n=14
Leaflets 5-7, 1-4 cm. long, serrations coarse and acute. Twigs with weak, rarely flattened infrastipular prickles. Stems 1-3 m. tall. [stamens ave. 65]*
ee
R. macounii
2n=14
Leaflets 7-11, usually under 2.5 cm. long. Twigs gristly or unarmed. Habit strict. Prairie form, usually less than 1 m. tall.
dd Sepals 2-4 mm. wide. Buds ovoid.
f Small-flowered western roses with arching branches. Leaflets ovate, finely serrate, somewhat cordate at base. Flowers usually in corymbs. Buds ovoid.
g
R. pisocarpa
2n=14
Stems slender, sparingly armed. Serrations fine and crenate (av. no. 15). Petals 15 mm. long. Sepals narrowed at base. Flowers on laterals only.
gg
R. californica
2n=28
Stems coarse, often bristly and prickly. Petals 20 mm. long. Sepals slightly narrowed at base. Serrations 10-20 (av. 14). flowering on long laterals and terminally on turions.
[stamens ave. 90]*
ff
R. X michiganensis
2n=14
Large flowered roses of Great Lakes region. Coarse, strict habit with scattered, flattened prickles. Leaflets oval to obovate. Teeth ascending, 7-28 (av. 17). Petals 2-2.5 cm. Stamens 120-150.

*Erlanson: Revision of genus Rosa (1934)
  Stamens
ave. no.
acicularis (hexaploid) 100
acicularis (octoploid) 75
arkansana 120
blanda 115
californica 90
carolina 105
gymnocarpa 57
minutifolia 45
nutkana 100
palustris 200
pisocarpa 75
setigera 212
stellata 175
virginiana 140
woodsii 65
yainacensis 70