Senna rostrata (Mart.) H.S.Irwin & Barneby

Authors

Howard S. Irwin, Rupert C. Barneby

Authority

Irwin, Howard S. & Barneby, Rupert C. 1982. The American Cassiinae. A synoptical revision of Leguminosae tribe Cassieae subtrib Cassiinae in the New World. Mem. New York Bot. Gard. 35, part 2: 455-918.

Family

Caesalpiniaceae

Scientific Name

Senna rostrata (Mart.) H.S.Irwin & Barneby

Type

Lectoholotypus, cult. VII. 1827 in hort. monac. from seed collected in Brazil (Martius 1544, Cassia saltuum nom. nud.), M! para- typus, Martius 1381, "in deserto Minarum Generalium ad Contendas ... in caldario floruit mense Jan. 1822," M!-C. biflora var.

Synonyms

Cassia rostrata Mart., Cassia biflora var. rostrata Benth., Cassia bicapsularis var. rostrata Benth.

Description

Species Description - Shrubs 1-5 m, in aspect and most details resembling coarse, large-fld S. pallida, the smooth green, angulately ribbed, freely forking hornotinous branchlets and lf-stalks at least thinly, sometimes densely pilosulous with fine whitish spreading- ascending hairs up to 0.2-0.5 mm mixed with random thickened livid ones, the pallid glaucescent foliage subconcolorous and appearing glabrous but the lfts often minutely ciliolate and rarely pilosulous beneath, the inflorescence of 2-fld racemes mostly axillary to recent lvs, late in season becoming subcorymbose and exserted. Stipules erect herbaceous narrowly linear-attenuate 4-11 x 0.25-0.6 mm, glabrous, caducous. Lvs 4.5-11.5 cm; petiole including moderately dilated pulvinus 12-22(-26) mm, at middle 0.5-11.5 mm diam, prominently 3-ribbed dorso-laterally and deeply 2-sulcate between the ribs, openly sulcate ventrally; rachis 3-5.5 cm; petiolar gland between proximal pair sessile or shortly stipitate 2-3.5 mm, the stipe when present puberulent, the glabrous compressed livid or orange body in profile obliquely obovate acute (1-)1.1-2.5 mm wide; sometimes similar smaller glands at 1-2 pairs next following; lfts 4-8 pairs, ascending from rachis face upward on linear pulvinule 1.2-2 mm, slightly accrescent upward, in outline obovate, oblong- obovate or broadly oblanceolate, obtuse or shallowly emarginate, muticous or minutely mucronulate, the distal pair (14-) 17-32 x (6-)8-15 mm, 1.7-2.4 times as long as wide, at base asymmetrically rounded, the membranous pallid margin plane or incipiently revolute, the midrib immersed above, cariniform beneath, the 6-8 pairs of camptodrome secondaries either immersed or faintly prominulous on either face. Peduncles 1.8-3.8 cm; racemes (1-)2-fld, the axis 0, the pedicels quasi-dichotomous; bracts lanceolate 2-4 mm caducous; pedicels 1.8-3 cm, subtended laterally at base by a sessile gland, in fruit abruptly bent shortly below hypanthium; fl-buds globose glabrous; sepals fuscous-green with submembranous or petaloid margins, strongly graduated, all obovate-orbicular, the innermost at least twice as long as outermost, 10.5-14 mm; petals yellow, puberulent externally at claw or to middle, strongly heteromorphic, 3 adaxial relatively short, ovate or oblong- obovate beyond the slender claw, the 2 abaxial heteromorphic, one like the adaxial but ampler, the other (alternately right and left) sessile very obliquely reniform 27-33 mm, folded to enclose the longest stamens; androecium glabrous, the filaments free, of 4 median stamens 1-1.8 mm, of 2 abaxial 3.3-7 mm, of one (lateral) abaxial 6-9 mm, the anthers of 4 median stamens oblong, slightly incurved 5-8 mm, with divaricate or infraterminal, very short beak opening by 2 parallel slits, those of 3 abaxial ones lunately incurved, the body 6.5-9 mm abruptly contracted into an erect tubular beak 3-4 mm, this opening by a terminal pore often divided by a slender septum; ovary white-strigulose; style 1-1.5 mm, at incurved apex ±0.35 mm diam; ovules 44-56. Pod erratically spreading-ascending or pendulous, the stipe (6-)7-11 mm, the linear compressed straight or slightly curved body (4.5-)6.5-11 x 0.65-0.8 cm, the papery valves becoming fuscous or nigrescently castaneous, delicately cross- venulose, elevated over the seeds in the form of low transverse ridges 1.5-2 mm wide; seeds narrowly obovoid, irregularly compressed or compressed-subquadrangular 3.5-4.4 x 1.4-2.3(-2.6) mm, the testa pale brown dull crackled, the elliptic areole (sometimes on the narrower faces of the seed) 1.2-1.5(-1.8) x 0.40.6 mm.-Collections: 27.

Distribution and Ecology - Stream-banks, pebbly riverbeds, woodland margins, becoming locally plentiful in disturbed cerrado or cerradao and persistent in pasture thickets and hedges, ±250-700 m, local, best known from the middle Sao Francisco valley in lat. 15°- 19°S, in centr. and n.-w. Minas Gerais and extreme s.-centr. Bahia (Urandi), extending e. of the crest of Sa. do Espinhaço to upper Rio Araguai (Minas Novas) and interruptedly w. into the valley of Rio Paranaiba in the Triangulo Mineiro (Tupaciguara) and s.-w. Goias (Jatai); an old record from Paraguay, without exact data of provenance (Fleischer s.n., P), requires confirmation.-Fl. IV-VIII(-IX).

Discussion

Senna rostrata resembles some broad-fruited North American form of S. pallida and was interpreted by Bentham as an outlying Brazilian variety of the equivalent Cassia biflora. Its pod, however, differs from that of S. pallida sens, lat. in having about fifty seeds crowded into a pod only about 7-11 cm long. In consequence the seed-locules become at least twice as wide as long and each seed, confined within its narrow stall, assumes a narrowly oblong-obovoid, compressed-subquadrangular form never encountered in S. pallida. This peculiar fruit, which suggests that of sympatric S. acuruensis rather than that of distantly allopatric (trans-Amazonian) S. pallida, entitles S. rostrata to the specific rank in which Martius originally described it. Within its own range S. rostrata can be mistaken only for the species next following, S. aversiflora, which see for comment.

Distribution

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