Bull. Torrey Botanical Club 74(3): 250-254 (May, 1947)

HIPPEASTRUM SOLANDRIFLORUM: ITS CHROMOSOMES
J. T. BALDWIN, JR. AND BERNICE M. SPEESE

Hippeastrum solandriflorum (Lindl.) Herb. is found from Brazil to Colombia and the Guianas (Macbride 1936) and, according to the interpretation of Herbert (1837), occurs in several varieties. It was introduced into cultivation in 1820 (Baker 1888) and has been used to a considerable extent in wide crosses, as have many representatives of the genus. Indeed Bailey (1938) states: "Most of the hippeastrums in cultivation are probably hybrids."

E. P. Killip identified Baldwin 3099, now in the U. S. National Herbarium, as H. solandriflorum: in flower. September 26. 1943. Braco, Rio Arinos, Matto Grosso, Brazil. The specimen rather well matches plate 3771 in Curtis's botanical magazine for 1840; that illustration is based on a collection made by Schomburgk in British Guiana. In May, 1946, a bulb from the Rio Arinos produced a flowering plant (fig. 1) under greenhouse conditions in Virginia, and, after the scape had withered away, gave rise in September, 1946, to a pair of narrow leaves edged with red. The mature capsule was reddish. Seedlings were grown from that plant.

1 It is worth of record that in September and October, 1943. Arachis was observed in flower on the outskirts of Rosario Oéste and also where the road leading northward from that town crosses the rim of the Amazon Basin. The plants of that rim seem in great measure different from those constituting the flora of the regions to the north and south of the rim. On December 3, 1943, in Matto Grosso, flowering specimens were obtained for A. marginata Gardn. at Tres Lagóas (Baldwin 3139), for A. Diogoi Hoehne at Campo Grande (Baldwin 3140), for A. marginata Gardn. at Corumbá (Baldwin 3141): identifications were made by F. C. Hoehne and E. P. Killip. The two collections designated A. marginata are of at least varietal difference. The specimens are in the U. S. National Herbarium. The subterranean fruit of Arachis, like the pronounced underground development of Macrosiphonia longiflora (Desf.) Muell. Arg., of Anacardium pumilum St. Hil., and of many other plants of that region, is apparently an adaptation to dryness. Fire may well have served as an agent of selection.

The senior author found H. solandriflorum at three places in Matto Grosso: at Braco, in a sandy area near the Rio Arinos and where grasses. sedges, and trees (among others Hancornia speciosa Gomes) are scattered; shortly downstream from Salto Bello on the Rio Sacre; and near Rosario Oéste, across the southern rim of the Amazon Basin, in sandy soil that becomes closely packed when dry and where Arachis sp. grows.1 The hippeastrum was in blossom in September and October, 1943. The flowers were extremely showy. No leaves were present. Populations were large. In two years (1942-1944) of almost continuous travel throughout the Amazonian region and in some of the country immediately south of the Basin, no more impressive assemblages of bulbous plants than these were seen, unless, perhaps, the stands of Zephyranthes along the Rio Cuyabá be excepted.

The perianth of H. solandriflorum is greenish yellow and reaches a length of eight inches. Two or four flowers are borne on a scape, which may attain a height of two and a half feet. The flowers are at first erect but with maturity turn downward. The spathe soon wilts. Leaves are produced later and may reach a length of one and a half feet (Baker 1888): those of our plant are in November, 1946, not yet six inches long.

FIGS. 2-4. Chromosomes of Hippeastrum solandriflorum, x 1100. FIG. 2. Metaphase from root of Rio Arinos plant with chromosomes distributed in drawing: 2n=22.
FIGS. 3, 4. Alignment of metaphase chromosomes of two seedlings of Rio Arinos plant. Figure 3 has unequal pair of chromosomes present, as in parent. Figure 4 has no unequal pair of chromosomes.

Because the Rio Arinos collection had not been "contaminated" through cultivation, it was decided to investigate the chromosomes of that plant and of some of the seedlings raised from it. Preparations were made by the junior author. Roots were treated with colchicine, fixed in Carnoy's solution (3 absolute alcohol: 1 chloroform: 1 glacial acetic acid), and smeared in propiocarmine.

H. solandriflorum from the Rio Arinos has a 2n-number of 22 (fig. 2). The plant investigated has one unequal pair of chromosomes. Five of the seedlings grown from that plant have been cytologically studied. Four of them are like the parent, with three pairs of chromosomes in the A group which has a short short arm), four pairs in the B group (with a longer short arm), three pairs of approximately isobrachial chromosomes in the C group, and an odd pair with one chromosome of the B type and one of the C (fig. 3). Classification into groups is arbitrary but convenient. Obviously, chromosomes in different roots and at different mitotic stages exhibit varying degrees of contraction when treated with colchicine. The fifth seedling has no odd pair of chromosomes (fig. 4): three pairs are in group A, four in group B. four in group C. If additional seedlings were studied, individuals with five pairs of B-type chromosomes would probably be encountered. Similarly: if the cytological structure of the Rio Arinos population of H. solandriflorum were to be analyzed with respect to the classification of chromosomes given here, it would be expected that a great—but unpredictable—percentage of the individuals would have a pair of chromosomes made up of B and C members.

Not many reports of chromosome numbers for Hippeastrum have been made:

  2n  
H. rutilum 44 Satô (1938)
H. rutilum fulgidum 24(?) Heitz (1926)
H. vittatum Herb. 46 Nagao & Takusagawa (1932)
" 44 Inariyama (1937)
" 44 Satô (1938)
H. hybridum 44 Inariyama (1937)

Inariyama (1937) and Satô (1938) suggested that their plants were tetraploid; the latter author classified the chromosomes as to types. H. solandriflorum from the Rio Arinos is accordingly diploid. A program of hybridization based upon a cytological knowledge of the various species of Hippeastrum should be most productive both of scientific and of horticultural results.

SUMMARY

Populations of Hippeastrum solandriflorum (Lindl.) Herb. were observed at three places in Matto Grosso, Brazil. A single plant from the Rio Arinos was cytologically studied. It is diploid with a 2n-number of 22 chromosomes, which can, on the basis of centromere location, be arbitrarily grouped into classes A, B, and C; one chromosome pair, with B and C members, is unequal.


FIG. 1. Hippeastrum solandriflorum (Lindl.) Herb.