Cassiinae pt 1 NY-Botanical_gardens_Vol. 35_1 - Copy.pdf - Antbase

254 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN [VOL. 35
throughout the year especiaUy in wet periods, in s. BrazU and Argenrina mostly
X-V.—Hediondilla; matapasto; charamazca (Michoacan).
Our concept ofS. obttisifolia is essentially that of Brenan (1958, I.e.), who also
examined the nomenclature and rejected a faulty typification by De Wit; in this
place we can add only some comments on internal variation in the New World.
The vernacular names Hediondilla and Matapasto provide a sort of shorthand
description of this weedy malodorous senna which, like many other plants that
have become, as h were, commensal with man, is geneticaUy complex and phe-
neticaUy heterogeneous. Three chromosome levels have been reported in S. ob­
tusifolia, but we have not learned to relate this to any phenetic formula or indeed
to recognize them in dried specimens. Growth form is known to be potentially
hereditary, for whUe in Texas the senior author grew side by side from seed
strains of S. obtusifolia, one of which, originating in Texas, maintained the erect
habit of its parent and flowered in late summer, while the other, originating on
the white sands of the Guyana near-interior, remained diffuse like its parent and
faUed to flower at all when translated northward through 30 degrees of latitude.
Moreover it seems probable that small generic differences can be handed down
indefinitely from one generarion to the next, for the flower is commonly, perhaps
always, fertUized in late bud, the style being then curved inward so as to present
the stigmaric cavity direcriy into the face of the precociously dehiscent anthers.
From early times it has been known that the petiolar glands of S. obtusifolia
may be either solitary between the first pair or one each between the first and
second pairs of leaflets; and Bentham wondered (1871, sub C. tora) whether there
might not be two real races different in length and curvature of the pod, a feature
that had been supposed, as we now know erroneously, to distinguish S. obtusi­
folia from S. tora. In America a second gland is relatively rare and of sporadic
occurrence through the range of the species; plants with or without it may occur
in the same habitat, without relation to other variable features. The pod and its
seeds, however, do show some interesting correlations with distribution. On the
Pacific coast of Mexico and southward through Central America, Colombia, Ecuador
and Venezuela, the pod is apparently always narrowly needleUke,
(2-)2.5-3.5 mm diam when fuUy ripe and often strongly curved out- and down­
ward. In pods of this type the seed locules are much longer than wide and the
oblong-cyUndroid seed Ues almost vertical along the pod's long axis. Throughout
United States and the West Indies the pod is broader, 3.5-6 mm diam when fully
ripe and on the average less curved; its locules are about 1-1.5 times as long as
wide, housing compressed-rhomboid seeds obhquely tUted across the pod's long
axis. In the Guianas and Amazonia, eastern Brazil and Argentina, a narrow pod
is prevalent, but a broad one appears at scattered points, perhaps chiefly suburban.
On the other hand broad pods alone are on record from Bolivia and Par­
aguay. Whether these two fruiting types had originally discrete ranges which have
become obscured by artificial dispersal we cannot now teU. And there are indi­
vidual specimens with pods ±3.5 diam which would be hard to place in either
category. The width of the pod has a bearing on the question of origin ofthe now
almost pantropical S. obtusifolia, which we suppose, following Irwin & Turner
(1960, p. 316), to be aboriginally neotropical. All African specimens of which
good fruit has been avaUable for study have the broad pods of AntiUean or United
States S. obtusifolia, which suggests that the African races of the species are
derived from Caribbean stock. The Indian, Indomalayan and Chinese material
that we have seen is of the same type, and could have been carried eastward
from Africa. But the Philippine form of S. obtusifoUa has the needlehke pod of
the plant prevalent in Pacific Mexico, and we cannot help wondering whether it