Monographs Details: Cassia cytisoides DC. ex Collad.
Authors:Howard S. Irwin, Rupert C. Barneby
Authority: Irwin, Howard S. & Barneby, Rupert C. 1978. Monographic studies in Cassia (Leguminosae, Caesalpinioideae). III. Sections Absus and Grimaldia. Mem. New York Bot. Gard. 30: 1-300.
Description:Species Description - Shrubs and small trees (0.5-)1-3(-4) m, with short crooked blackish lenticellate trunks and often tortuously divaricate branchlets clad at summit with ample, usually much simplified, leathery and veiny, when old often dorsally glaucescent foliage, appearing glabrous, sometimes fully so, but the stipules, bracts and sepals commonly ciliolate, and the branchlets with associated If-stalks sometimes densely minutely pilosulous, exceptionally subsetulose (but apparently never glutinous), the subcorymbose racemes of few, long-pedicelled fls all axillary and immersed in foliage or sometimes aggregated into a dense terminal leafless panicle.
Stipules erect, appressed to stem (sometimes concealed behind the swollen pulvinus), triangular-subulate, 0.4-1 (-1.2) mm, tardily deciduous.
Lvs mostly widely ascending to horizontally divaricate, some deflexed, sessile or petioled,1.5-7 cm; pulvinus moderately dilated, castaneous or livid, not or little wrinkled when dry, 1-2 mm; If-stalks 0-3.5 cm, when developed 0.7-1.2 mm diam, openly and shallowly sulcate ventrally and charged in the groove with 1-3 (-4) sessile, depressed, elliptic or circular glands (0.5-) 0.8-3 mm diam, these situated either (in sessile leaves) between pairs of Ifts or (in petiolate Ivs) below the single pair, or (in sessile bifoIiolate Ivs) between the two Ifts, in any case produced at apex into a minute appendage (sometimes charged with an additional smaller gland); Ifts 1-3 (exceptionally 4) pairs, when more than one pair the lowest commonly proportionately wider but either longer or shorter than the rest, the first pair (of sessile Ivs) amplexicaul, the rest tilted forward from rachis, turned half face to face on dilated, wrinkled pulvinule (0.8-) 1.2-2 mm, all in outline varying from suborbicular-reniform to obliquely obovate-cuneate, in one var. oblanceolate, at apex very obtuse or subtruncate, not mucronate, at base varying from broadly obliquely cuneate to sinuately truncate or asymmetrically shallow- cordate,1.2-5.5 x (3.5-)0.8-6.5 cm, the plane margins entire, subcorneous, the blades coriaceous bicolored, above dull or sublustrously olivaceous, beneath dull but paler olivaceous or variably purple-tinged, often strongly glaucescent in age, all palmately 3-7-nerved from the pulvinule, the midrib giving rise, at or above middle, to 2-4(-5) pairs of major secondary veins, these all prominulous on both sides but coarser and more sharply elevated beneath, the connecting ter- tiaries few and irregular, not anastomosing to form a regular mesh.
Racemes (1 -)2-7-f ld, the slender axis and short peduncle together (3-)8-25 cm, the axis charged between the pedicels with scattered glands of same type as on the If-stalks, the 1-3 simultaneously expanded fls usually elevated above the succeeding buds; bracts deltate to broadly subulate, 0.7-1.8 mm long, persistent; pedicles at anthesis flexuously ascending, 1.8-3 cm, in fruit stiffly incurved-ascending, bracteolate 3-12(-20) mm below calyx; bracteoles resembling bracts, slightly smaller, tardily deciduous; buds plumply ovoid or ellipsoid, obtuse, except for sometimes minutely ciliolate sepals glabrous, not glutinous; sepals subpetaloid, yellowish or brownish, elliptic or elliptic-oblanceolate, obtuse, of unequal lengths, 7.5-11 x 3.5-8 mm; petals yellow, the four plane ones widely incurved-ascending at anthesis, obovate-cuneate or flabel- late, 2 larger and 2 smaller, the largest variable in size, up to 12-25 mm (1.2-2 times longer than sepals), the fifth petal falcately lanceolate, a little longer than the rest, coiled; ovary glabrous or rarely ciliolate along the sutures; ovules (7-)8-13.
Pod broadly linear-oblong or when short broadly oblong-elliptic, straight or a little curved downward, (3-)4-7 x (0.8-)1-1.3 cm, the brown or reddish-brown, ultimately nigrescent, sublustrous but not glutinous, glabrous valves septate internally between the seeds; seeds subquadrately compressed-pyriform, 5.7-7 x 3.5-4 mm, the dark brown, dull testa lineolate-pitted.
Our concept of C. cytisoides is here expanded to include three species maintained by Bentham (1870, 1871); the still poorly known typical C. cytisoides, which has sessile 6- foliolate leaves; C. brachystachya, which may have either sessile and mostly 4-foliolate or (var. unijuga) petioled and bifoliolate leaves, and C. blancheti, with sessile bifoliolate leaves.
Our knowledge of the last two has grown considerably since Bentham's day, and the exact number of leaflets is now seen as not immutably fixed. Already among some duplicates of Riedel's original C. brachystachya not seen by Bentham there were a few 6-foliolate leaves, and we have one example displaying 4-foliolate leaves in a specimen of otherwise well- characterized C. blancheti. The difference between a sessile leaf, in which the first (or only) pair of leaflets arises directly next to the leaf-pulvinus, and a petiolate leaf, from which the first pair has seemingly been suppressed, was even by Bentham regarded as only of varietal importance. Until lately C. cytiosoides seemed safely distinct from C. brachystachya and C. blancheti collectively in the combination of more numerous and simultaneously narrower leaflets, none obliquely reniform and all longer than wide, but the var. micrantha, described below, has only two pairs of the same type of leaflet and forms a connecting link. It should be emphasized that the texture and venation of the leaflets, the organization of the racemes, and the form of flowers, pods, and seeds, remain virtually uniform throughout the series of leaf-modifications on which the supposed species ultimately rest.
The leathery, often glaucous, palmately rather than pinnately veined leaflets of C. cytisoides are unusual in Cassia but find a singular parallel in the Mexican Acacia crassifolia A. Gray where they are, however, arranged biplinnately as single pairs terminal to a single pair of pinnae.