Cassia conferta Benth.

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

Scientific Name

Cassia conferta Benth.

Type

Typus infra sub var. conferta indicatur.

Synonyms

Cassia conferta Benth. var. conferta

Description

Species Description - Shrubs and undershrubs variable in habit and stature, (0.3-)0.6-2.5 m, the trunks of truly fruticose forms developing longitudinally fissured bark, the stems or branchlets of the year stiffly virgate and clad in upwardly imbricated thatch of 2-4-foliolate leaves, appearing glabrous throughout and sometimes truly so, but the young stems, axes of inflorescence, sepals, and sometimes also the lf-stalks and lft-margins puberulent or minutely villosulous, the branchlets and lft-margins also exceptionally glandular-setulose, the plane leathery lfts concolorous or almost so and except for the dorsally carinate midrib subequally venose both sides, the racemes of variable length terminal to the main stem and sometimes to few or many short lateral and subterminal branchlets, forming a corymbose or sometimes thyrsiform-paniculate inflorescence shortly exserted from the foliage. Stipules erect, firm, subulate or setiform, 0.3-3 mm, sometimes concealed between the stem and the pulvinus, persistent or tardily deciduous. Lvs subvertically ascending along the stems, (1.2-) 1.5-7(-9) cm, shortly petioled or rarely sessile, subuniform in size or somewhat diminished distally; pulvinus ovoid-ellipsoid, slightly or strongly dilated, 1-3 mm; petiole (excluding pulvinus) usually 1-5 mm, 0.4-1.3 mm diam, exceptionally lacking or up to 9.5 mm long, shallowly open-sulcate ventrally; rachis 0-15(-19) mm; lfts 1 or 2 pairs, commonly 2 in all but the earliest and uppermost leaves but exceptionally 1 in all or most lvs, when 2 pairs the distal larger, all subvertically ascending, turned half face to face on dilated, when dry wrinkled pulvinule 0.5-1.4 mm, in outline subsymmetrically oblanceolate or elliptic-oblanceolate to narrowly obovate-cuneate, truncate, obtuse or emarginate but always minutely mucronate by the excurrent midrib, (0.8-) 1-4.5(-6) x (0.3-)0.4-1.8(-2.4) cm, at base either cuneately attenuate or abruptly contracted into the pulvinule, the margins entire, plane, sharp-edged, the blades subcoriaceous, dull olivaceous and glabrous both sides, carinate dorsally by the midrib, the venation of 4-7 major secondary veins equally prominulous both sides, the tertiary reticulate venation present or not, if present equally pronounced above and beneath. Racemes commonly short and dense, terminal to branchlets, little (or rarely elongating and much) exserted, the 2 or more simultaneously expanded flowers elevated about to level of succeeding buds, but occasionally standing well below them; bracts submembranous, triangular-subulate, 1-2.2 mm, caducous from under the swelling buds; pedicels ascending, 1.2-2.9 cm, bracteolate 0.5-2.5(-4.5) mm below calyx; bracteoles resembling bracts, 0.6-1.6 mm, deciduous; buds ovoid or ovoid-ellipsoid obtuse, commonly puberulent but not glandular, rarely glabrous; sepals at anthesis widely expanding, yellowish sometimes reddish-brown, oblong-elliptic obtuse, (6-)7-11 mm, the inner with sharply defined pallid-membranous margins; petals usually entirely yellow, sometimes at base tinged with orange, campanulately expanded, the 4 similar ones obovate-cuneate to spatulate, to 9.5-16 mm; ovary usually densely puberulent but never setulose, rarely glabrous; ovules 4-7(8). Pod in outline oblong, linear-oblong, or oblong-elliptic, almost straight, (2-)2.5-4.5(-5) x 0.6-0.85(-0.9) cm, the valves either greenish-stramineous or reddish-brown and ultimately nigrescent, thinly puberulent (especially along the sutures) or sometimes glabrous; seeds obovate in outline, 3.8-4.5 x 2.1-3.3 mm, the testa atrocastaneous, lustrous, minutely cross-crackled and faintly lineolate.

Discussion

A species traditionally and no doubt correctly associated with C. ochnacea, which it resembles in the blunt flower-buds and more importantly in the plane coriaceous leaflets equally veiny above and beneath, but differing in the more crowded, subvertically ascending leaves antrorsely imbricated along the branches and the mostly narrower leaflets, commonly two, rarely all one, but never either three or four pairs. So far as known, the ranges of the two species are vicariant, a line drawn through Serra do Espinhaço at 18° 30' S sundering C. ochnacea var. ochnacea to the south from C. conferta var. conferta northward. Morphologically these are abruptly separable by shape of leaflets alone, those of var. ochnacea being asymmetrically rounded at base, those of var. conferta symmetrically attenuate, a difference, it must be noted, that does not hold for other, distantly allopatric varieties of C. conferta. The latter's main range lies to the west of Rio Sao Francisco mainly in Goias, wheras C. ochnacea (disregarding its rare var. speluncae) is endemic to the southern half of Serra do Espinhaço entirely within Minas Gerais.

As already known to Bentham a century ago, C. conferta is like C. ochnacea a polymorphic species, varying in stature, habit, and form of leaflets, which may be either simply penninerved or intricately reticulate. Bentham assessed the larger, smaller, and intermediate leaf-sizes as taxonomically insignificant, but modern collecting has brought them into sharper focus and related them to significant geographic patterns. As might be expected, the populations of C. conferta in Serra do Espinhaço, are different from the rest, separated as they are by the width of the Sao Francisco valley. In Goias and immediately adjacent Minas we can now discern one widespread and two highly localized varieties.

In the protologue Bentham dates his first use of the name C. conferta to the year 1845, when he was studying the cassias of the St. Petersburg herbarium. Clearly this connects it with the piece of Riedel 487 now at Kew, which has exceptionally small crowded leaflets to match the epithet, and has determined our choice of lectotype and, as a consequence, the restricted application of the term var. conferta.

Key to varieties of Cassia conferta

1. Lfts small, mostly 1-2.5 cm, at base cuneately narrowed on both sides into the pulvinule; mature stature distinctly fruticose, the old stems developing fissured bark; central Minas Gerais (Sa do Espinhaco) and very local in e.-centr. Goias (Chapada dps Veadeiros).

2. Branchlets glabrous or minutely puberulent; lfts penninerved, the tertiary venation immersed; fls relatively small, the sepals mostly 7-9 mm, the petals 9.5-12 mm long; Sa. do Espinhaco, Minas Gerais.

117a. var. conferta

2. Branchlets densely short-villosulous; lfts reticulate, the tertiary venules prominulous both above and beneath; fls larger, the sepals 9-12 mm, the petals to 14-16 mm; local in Chapada dos Veadeiros, e.-centr. Goias.

117b. var. simulans

1. Lfts larger, mostly 1.8-4.5 cm, the largest of a given plant commonly 2.5 cm or more, all in any case abruptly rounded or subcordately contracted into the pulvinule; Goias and extreme w. Minas Gerais. Mature stature various.

3. Lfts appearing smooth, the pinnate secondary venation faintly prominulous but the tertiary immersed, the blades therefore not reticulate; mature stature fruticose, like var. conferta and var. simulans.

117c. var. machrisiana

3. Lfts elaborately reticulate both sides, the secondary and tertiary venation subequally prominulous; mature stature not or scarcely fruticose, the flowering stems virgately erect and ascending from a xylopodium or lignescent caudex; widespread over the Amazon-Paranaiba-Sao Francisco watersheds, across s.-centr. and s.-e. Goias through Distrito Federal into n.-w. Minas Gerais.

117d. var. virgata

Distribution

Goiás Brazil South America| Minas Gerais Brazil South America| Brazil South America|