Senna ripleyana (H.S.Irwin & Barneby) H.S.Irwin & Barneby
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Authors
Howard S. Irwin, Rupert C. Barneby
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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.
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Family
Caesalpiniaceae
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Scientific Name
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Type
Holotypus, NY!
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Synonyms
Cassia ripleyana H.S.Irwin & Barneby, Cassia ripleyi H.S.Irwin & Barneby ex Isely
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Description
Species Description - Dwarf, loosely cespitose subacaulescent and shortly caulescent perennial herbs from woody taproot and ultimately a branched caudex, including the exserted peduncles 4-14 cm, pilosulous throughout with coarser, antrorsely incurved-as- cending hairs less than 1 mm and a few weak spreading filiform ones up to ±2-2.5 mm, the 1 pair of lfts ashen beneath, greener above, pubescent on both faces, the l(-2)-fld axillary racemes exserted from the tufted foliage. Stipules erect often recurved at tip, narrowly linear-caudate (4-)6-10 mm, strongly 1-nerved, persistent. Lvs 1-5 cm; petiole stiff l-2.5(-3.2) cm, at middle 0.4-0.5 mm diam, ribbed dorsally, the ventral groove almost closed; petiolar gland divaricate from between the 2 lfts, stipitate, in profile 0.7-2.7 mm, the slenderly lance-fusiform acute head 0.1-0.2 mm diam; lfts oblong- or obliquely obovate-elliptic obtuse mucronulate or subapiculate (6-)8-20 x 3-10 mm, at base broadly cordate on proximal and cuneate on distal side, the margin plane, the slender midrib prominulous beneath, the blades otherwise veinless. Peduncles stiffly erect or in fruit declined, 2.5-6 cm, 1-, rarely 2-fld; bracts lanceolate or triangular-subulate 1-2.5 mm, early dry deciduous; mature pedicels 5-10 mm; fl-buds nodding, obovoid pilosulous; sepals of subequal length 5-6.5 mm, the outer elliptic-oblanceolate the inner obovate, all membranous-margined; petals yellow drying whitish brown-veined, glabrous, spatulate-oblanceolate beyond the short claw, 8.5-9.5 x 5-6 mm; androecium of S. bauhinioides, the fertile anthers ±3-3.5 mm; ovary densely white-pilose; style filiform 3-3.5 x 0.2-0.3 mm, decurved from ovary and thence incurved to the truncate stigma; ovules 18-28. Pod obliquely ascending sessile, in profile narrowly oblong or oblong-oblanceolate, straight or slightly incurved (13-) 15-24 x 5-8 mm, abruptly subulate- beaked, strongly turgid, the ripe valves papery brown, paler along the sutural margins, faintly corrugate over the seeds, pubescent with short appressed and stiffly ascending setules up to ±0.7-1 mm, dehiscent downward along both sutures, narrowly gaping to release the seeds; seeds closely stacked in 2 interdigitating rows, basically paddle-shaped but often distorted by crowding, the well- formed ones ±2.5-3 x 2 mm, the testa pinkish-brown, olivaceous or ochraceous, smooth and highly lustrous, not wrinkled, the elliptic areole 0.45-0.7 x 0.3-0.4 mm.—Collections: 5.
Distribution and Ecology - Gravelly hilltops and flats in arid grassland and Larrea desert, 1400-1700 m, apparently rare (but perhaps overlooked or passed over as S. bauhinioides), centr. Chihuahuan Desert from trans-Pecos Texas (Brewster Co.) to s.-e. Chihuahua and n. Zacatecas.—Fl. VII-X.
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Discussion
Clearly related to sympatric S. bauhinioides, but distinguished by the cespitose habit, wiry subscapiform peduncles, filiform style and lustrously smooth olivaceous to pinkish-brown seeds.
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Distribution
Texas United States of America North America| Chihuahua Mexico North America| Zacatecas Mexico North America|