Cassia densifolia

Title

Cassia densifolia

Authors

Howard S. Irwin, Rupert C. Barneby

Scientific Name

Cassia densifolia Benth.

Description

81.  Cassia densifolia Bentham in J. Bot. (Hooker) 2: 80. 1840. — . from Pohl s Brazilian collection." — Holotypus, Pohl 5701, K (hb. Benth.)! = NY Negs. 1499. 6742, isotypus, NY! isotypus, numbered Pohl 983, LE!

Undershrubs with few mostly simple wandlike stems of 1-2 years duration erect and ascending from a xylopodium 5-12 dm, densely clad in short horizontally spreading lvs, except for the glabrous or subglabrous faces of the erratically setose-ciliolate leaflets in all parts densely minutely puberulent and except for the glabrescent calyx also viscid-setulose, densely so distally, the foliage concolorous, the inflorescence a terminal exserted, sometimes basally leafy-bracteate, narrowly thyrsiform panicle of racemes.

Stipules erect firm subulate or subsetiform, 1-3 mm, persistent.

Lvs heteromorphic, the lowest (commonly shed by anthesis) and those within or near the inflorescence smaller and simpler, those near middle of stems 3-7 cm, all stiffly divaricate from stem, very shortly petioled or subsessile; pulvinus firm, dilated but otherwise hardly differentiated, 1-1.5 mm; petiole 0-4.5 mm; rachis 0.7-4 cm, of most major lvs at least 2 cm, at middle of first segment 0.5-0.7 mm diam, tapering distally, narrowly 2-winged ventrally, the sulcus almost closed; lfts of most lvs 4-7(-8), of some early leaves only 2-4 pairs, commonly decrescent upward but sometimes the reverse, all divaricate from rachis and tilted, proximal margin edgewise to meridian, on ovoid when dry wrinkled pulvinule 0.4-0.8 mm, from ventral view appearing sessile, in outline broadly ovate or suborbicular, obtuse or obscurely emarginate, minutely mucronulate, (4-)5-24 x (2.5-)3.5-19(-21) mm, at base on proximal side broadly decurrent to the rachis, on distal side cordate, the plane entire or subcrenulate margin glabrous or weakly gland-setulose, the blades chartaceous, on both faces dull olivaceous glabrous or rarely puberulent dorsally along the veins, the midrib with 5-8 pairs of major secondary and at least some, often many tertiary venules prominulous on both faces, but often more sharply so beneath, forming a reticulum of plane areoles <1 mm diam.

Inflorescence a panicle (0.5-)1-3 dm long ± 0.5-1.5 dm diam composed of strictly ascending simple or weakly branched racemes, the primary axis a continuation of the current year's growth, the individual racemes 1-15 (-20)-fld, 2-10(-16) cm, the one expanded fl raised about to level of next bud; bracts submembranous, ovate or subulate, becoming dry, irregularly deciduous; buds ovoid, short-apiculate, puberulent at base, thence glabrescent, not setulose; sepals petaloid, ovate- elliptic obtuse, 8-9 x 4-4.4 mm; petals yellow, the four plane ones of nearly the same shape but one slightly larger, broadly ovate-cuneate or flabellate, up to 13-15.5 x 11-14.5 mm; ovary densely yellow-setose; ovules 4-6.

Pod oblong, 3-3.5 x 6-7.5 mm, the reddish-brown valves minutely viscid-puberulent and weakly hispid with yellow setae up to 1-1.5 mm; seeds 4.2-4.6 x 2.9-3.4 mm, the testa dark brown or almost black, not highly lustrous, faintly lineolate. — Collections: 4.

Cerrado, 1000—1100 m, apparently local, known only from Serras dos Cristais and da Tiririca along the boundary between s.-w. Goias and Minas Gerais, in lat. 16° 30—18' S. — Fl. IX-II.

One of the virgate cassias of the cerrado, with few tall stems clad in short, horizontally divaricate leaves, C. densifolia seems closely related to the vicariant C. brachyrachis, endemic to Distrito Federal immediately northward. Its foliage, however, is less modified by contraction of the rachis, the larger leaves becoming about three times as long, composed of twice as many pairs of leaflets, which are moreover reticulately venulose on both faces when adult, neither smooth above nor simply penninerved beneath. The two species are alike in so far as the leafy growth of the season goes out uninterruptedly into a leafless, more or less thyrsiform panicle of racemes. Of related species found within the range of C. densifolia, only C. polita and C. nummulariifolia are likely to be confused with it. The former has stems in the lower half glabrous and shining, and an irregularly corymbose inflorescence that develops independently of and much later than the leafy axis that bears it, while the larger flowers are borne on much longer pedicels. Similarly large, long-pedicelled flowers combined with procumbent or diffuse stems distinguish C. nummulariifolia decisively.