Monographs Details: Cassia chaetostegia H.S.Irwin & Barneby
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.
Family:Caesalpiniaceae
Synonyms:Cassia chaetostegia var. chaetostegia
Description:Latin Diagnosis - Cassia chaetostegia Irwin & Barneby, sp. nov., statura elata, stipulis elongatis setiformibus, foliolis multijugis secus rachin confertis simul ac resupinatim verticalibus utrinque pulchre reticulatis, necnon panicula parum exserta notabilis, a C. mollifolia caulibus elatis fruticoso- arborescentibus, inflorescentiae paniculatae nec simplicis axibus setulosis nec tantum villosulis, floribusque minoribus, a C. feliciana habitu florumque magnitudine comparabili imprimis panicula parva basi foliata nec laxe corymbosa nuda longe exserta absimilis.

Species Description - Virgate, densely leafy shrubs and treelets with 1 or few erect simple or distally few-branched stems, at anthesis (1-)1.5-2.5 m, either throughout finely pilosulous with erect hairs mixed, at least on stems, lf-stalks, and all axes of inflorescence, with minute yellow setules, or the lfts glabrous on one or both faces, the foliage concolorous, the inflorescence a terminal shortly exserted, compact, partly leafy-bracteate panicle of racemes. Stipules displaced outward or downward by the deflexed proximal lfts, green, pliant, linear- attenuate, (4.5-)5-12 mm, becoming dry fragile and then easily deciduous. Lvs ± heteromorphic, those low on the year's growth (often shed by anthesis) shorter and simpler than the rest, very short-petioled, all others sessile or almost so, divaricate or widely ascending from stem, 4-15 cm; pulvinus moderately dilated, commonly discolored but otherwise not differentiated, 1-1.8 mm; rachis almost as long as lf, at middle of first segment in dorsal view 0.5-0.8(-1) mm diam, 2-winged ventrally, the sulcus deep but almost closed; lfts of early lvs 3-8, of all adult sessile or subsessile cauline ones 10-21 pairs, of equal size or a little diminished upward, crowded along rachis, heteromorphic in attitude, the lowest 1-2 pairs deflexed toward, the lowest around the stem, the remainder divaricate from rachis, tilted edgewise to meridian, proximal margin up, on slightly turgid pulvinule 0.5-0.9(-1) mm, in outline varying from ovate or ovate-elliptic and apiculate to obovate-suborbicular and obtuse or (in lowest leaves) emarginate, 5-21 x 2.5-26 mm, all minutely mucronulate, at base cordate both sides but more deeply so distally, the glabrous or villous-ciliolate, sometimes also minutely setulose margins entire, plane or subinvolute, the adult blade firmly chartaceous, on both sides dull-olivaceous and finely pilosulous (exceptionally glabrate ventrally), the midrib above immersed, beneath sharply carinate, the 3-9 pairs of secondary and at least some, usually many tertiary connecting venules raised both sides to form an irregular but close reticulum. Inflorescence a compact, round-headed panicle of densely (2-)6-30-fld racemes ±9-14 cm diam, at base leafy-bracteate, thereafter leafless, the individual raceme-axis becoming 3-8(-10) cm; bracts submembranous, linear-lanceolate 2-3.5 mm, deciduous at anthesis; pedicels ascending 1.4-2.3 cm, bracteolate 0.5-6(-8) mm below calyx; bracteoles resembling bracts, deciduous; buds ovoid, shortly obtusely apiculate, at once thinly villosulous and sparsely yellow-setulose or merely puberulent; sepals widely ascending at anthesis, subpetaloid, yellow or greenish, elliptic, mostly obtuse, 8.5-11 x 3.4-3.8 mm; petals ascending at ±45°, yellow, the four plane ones broadly obovate-cuneate or flabellate, one slightly larger than the rest, 12-16.5 x 9-11.5 mm, the fifth half-ovate, 10-12 mm long, coiled; ovary viscid-villosulous and yellow-setulose; ovules 5-9. Pod 2-3.5 x 0.6-0.7 cm, densely pilosulous and the sutures, often the valves also, sparsely setulose or yellow-setose. Plate 11.

Discussion:

A tall shrubby or eventually arborescent cassia notable for the densely leafy virgate stems, the many pairs of reticulately veiny, resupinately vertical leaflets crowded along a stiffly divaricate rachis, and for the small terminal scarcely exserted, at least partly leafy-bracteate panicle developing with the leaves. The species appears closely akin to C. mollifolia, which differs in its much shorter, functionally herbaceous, simple stems arising from a xylopodium and passing upward into a simple raceme of larger flowers; and to C. feliciana, which it resembles in stature, but which differs in the far exserted, subumbellate and leafless panicle quite like that of C. orbiculata in ontogeny and facies. Typical C. chaetostegia, softly puberulent and only minutely setulose, with relatively small, mostly ovate leaflets villosulous on both faces is known only from a very small area around the source of Rio Sobradinho in Distrito Federal; a still poorly known form, described below as var. obolaria, different in the mostly round, coinlike leaflets glabrous both sides and on the average larger and more elaborately veiny, appears to represent the species on Chapada dos Veadeiros about 175 km to the north.

Key to the varieties of C. chaetostegia

1. Vesture of stems and lf-stalks predominantly villosulous, the fine gray hairs longer than the minute intermixed setules; lfts of adult lvs ovate, relatively small, less than 15 mm long, villosulous on both faces and villous-ciliolate, the major secondary veins 3-6 pairs; petals up to ± 13.5 mm; pod only minutely setulose; Distrito Federal.

84a. var. chaetostegia

1. Vesture of stems and lf-stalks both villosulous and setulose, either type of trichome predominating but of ± equal length; lfts of adult lvs suborbicular-emarginate, 1-2.5 cm diam, glabrous on both faces, erratically setose-ciliolate, the major secondary nerves 6-9 pairs; petals up to 16.5 m; pod thinly hispid with yellow setae up to ± 1.5 mm; Chapada dos Veadeiros, Goias.

84b. var. obolaria