Monographs Details: Senna paraënsis (Ducke) 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 1: 1-454.
Family:Caesalpiniaceae
Synonyms:Cassia paraensis Ducke
Description:Species Description - Coarse, ultimately suffrutescent, erect or diffusely ascending herbs at anthesis ±5-11 dm, softly pilosulous throughout with fine incurved short hairs but the angulate stems and some lf-stalks in addition hispid with slender erect sordid setae up to 1.2-3 mm, the foliage bicolored, the lfts dull dark (when dry brownish-) green above, pallid beneath, the 1-3-fld racemes axillary to cauline lvs, not or scarcely exserted. Stipules linear-attenuate, erect or incipiently falcate, 6-10 x 0.3-0.7 mm, at first herbaceous, early dry and deciduous before the lf. Lvs 3.5-8.5 cm; petiole including discolored but little swollen pulvinus 8-18 mm, at middle 0.6-1.2 mm diam, carinate dorsally, very narrowly obtusely margined and openly sulcate ventrally; rachis 6-16 mm, either longer or shorter than petiole; glands between proximal and second but apparently never between distal pair of lfts, sessile or almost so, slenderly lance-fusiform acute 1.2-2 x 0.15-0.3 mm; pulvinules 1.2-2 mm; lfts of almost all lvs 3 pairs, strongly accrescent distally, the distal pair broadly oblanceolate to narrowly obovate or elliptic-oblong- obovate, obtuse mucronulate 2.5-5.5 x 1-2 cm, 2-2.8 times as long as wide, at base cordate on proximal and cuneate on distal side, the midrib with 6-8 pairs of camptodrome (and rare intercalary) secondary veins faintly defined above, sharply prominulous beneath, the tertiary connecting venules finely evident beneath only. Peduncles 11-26 mm; raceme-axis 0-1.5 mm; bracts ovate 1.5-2 mm, early dry caducous; pedicels 12-17 mm; young fl-buds nodding subglobose, hispidulous throughout or at base only, the dorsally puberulent petals emergent well before anthesis; sepals moderately graduated, oblong-obovate, the long inner ones 5.5-6 mm, prominently 5-nerved from base, the nerves simple; petals of ser. Trigonelloideae, the slightly longer abaxial ones 10-13 mm; androecium glabrous except for sometimes puberulent filaments, these of 4 median stamens 1.2-2 mm, of 3 abaxial ones 2.5-3 mm, the anthers of 4 median stamens 3.5-4 mm, their very short biporose beak divaricate, those of 3 abaxial ones 4-5.8 mm, contracted into an almost erect beak ±0.7 mm, this obliquely biporose; ovary spreading- or ascending-pilose; style 2.5-3.8 mm, a little dilated upward 0.5-0.6 mm diam, incurved only at very apex where contracted into the oblique stigmatic cavity; ovules 28-32. Pod ascending and gently curved outward, narrowly linear 9-12.5 x 0.4-0.45 cm, contracted at base into a stout stipe 2-3 mm, at apex into the persistent style, bicarinate by the sutures, at first strongly compressed but bluntly subtetragonal at maturity, the interseminal septa ±4 mm apart, the locules ± as wide as long; seeds obliquely descending across the pod-cavity, ±4 mm long, the testa apparently atropurpureous lustrous, the oblong-elliptic areole ±2 mm.—Collections: 5.

Distribution and Ecology - Annually flooded savannas and river banks, below 100 m, apparently local in n.-e. Amazonian Brazil: Rio Branco near 2°30'N in Terr, do Roraima; and along the lower Madeira and Amazon rivers and the latter’s immediate tributaries from Itapiranga in e. Amazonas downstream to Almeirim in Para; disjunct on rio Yac- uma near 14°S,66°W in Beni, Bolivia.—Fl. VIII-II.

Discussion:As noted by Ducke, S. paraensis combines the pedunculate raceme and setose vesture of S. pilifera with the trijugate leaflets of S. obtusifolia or, we might add, of S. cobanensis, in both of which the racemes are subsessile. It is not reliably distinguished from S. pilifera, as Ducke thought, by flower-size, for the marginally sympatric (but consistently bijugate) S. pilifera var. sub glabra can have equally short sepals and petals. On the other hand the distantly allopatric S. cobanensis, which resembles S. paraensis not only in leaflet-number but also in the pod, really is larger-flowered, the longer petals almost always well over 15, not 10-13 mm long.
Distribution:Roraima Brazil South America| Pará Brazil South America| Beni Bolivia South America|

Narratives:Senna paraensis