Senna pilosior

Title

Senna pilosior

Authors

Howard S. Irwin, Rupert C. Barneby

Scientific Name

Senna pilosior (C.B.Rob. ex J.F.Macbr.) H.S.Irwin & Barneby

Description

82.  Senna pilosior (Macbride) Irwin & Barneby, Phytologia 44(7): 500. 1979. Cassia bauhinioides var. pilosior Robinson ex Macbride, Contrib. Gray Herb., n. ser. 59: 27. 1919—"TEXAS: Bofecillos Mts. [s. Presidio County], Sept., 1883, Havard, no. 14 . . . MEXICO: Torreon, Coahuila, Oct. 13-20, 1898, Palmer, no. 455; 75 miles southwest of Parras, Coahuila, May, 1880, Palmer, no. 2132."—Holotypus, Havard 14, GH! paratypi, Palmer 455, GH, NY, US! 2132, GH, US!—Cassia pilosior (Macbride) Irwin & Barneby, Sida 6(1): 10. 1965.

Cassia durangensis sensu Turner, 1959, p. 74, map 35 (Texas); Correll & Johnston, 1970, p. 788; Isely, 1975, p. 81, 198, 201, map 28 (Texas).

Cassia pilosior sensu Isely, 1975, p. 227.

Erect herbs from dark brown or blackish, sharply tapering taproot, monocarpic or sometimes persisting over winter to a second season, at anthesis (1-) 1.5-6.5 dm, the 1-several simple or few-branched stems with lf-stalks and axes of inflorescence densely pubescent throughout with a) a dense undercoat of short soft, loosely retrorse hairs mixed with minute yellow glandiform trichomes, b) stiffer ascending or incurved setules up to 0.4-1 mm, and c) few or many subhorizontal weak lustrous spiral setae up to 2-4 mm, the ample 2-foliolate lvs bicolored, the lfts densely antrorsely pilosulous on both faces, gray-silvery beneath and golden- tinged above, the few-fld racemes lateral and axillary to most major lvs, only late in season becoming subpaniculate.

Stipules loosely ascending-spreading, narrowly lance- or linear-caudate (3-)4-12 x 0.3-0.7 mm, at first herbaceous, early dry and fragile but only tardily deciduous.

Lvs (1.5-)2.5-7.5 cm; petiole including scarcely differentiated pulvinus 1-3.5(-4) cm, at middle 0.4-1.1 mm diam, the narrow shallow ventral sulcus concealed by pubescence; gland between the single pair of lfts, slenderly stipitate, in profile (0.7-)l-2.4 mm, the stipe pilosulous, the narrowly fusiform or ovoid- fusiform acute head 0. l-0.35(-0.4) mm diam; lfts broadly obliquely obovate or amply oblong-obovate obtuse mucronulate or shallowly emarginate, the larger of any plant (15-) 18-40 x 10-23 mm, (1.3-) 1.4-1.8 times as long as wide, at base deeply widely cordate on proximal side, the margin plane, the blade essentially veinless above, the midrib prominulous beneath and there giving rise on each side to 3-6 incurved-ascending secondary veins, these expiring well short of anastomosis.

Racemes loosely and shortly or subumbellately (2-)3-5(-6)-fld, the peduncle and axis together becoming 2.5-8.5 cm; bracts narrowly lance-acuminate or -caudate, early dry but long persistent, sometimes under ripe fruits; pedicels narrowly ascending, at full anthesis and afterward 6-15 mm; fl-buds horizontal or nodding, obovoid obtuse pilosulous and commonly also setose; sepals pale green, the slightly broader inner ones pallidly membranous-margined, all elliptic or obovate- elliptic obtuse, of subequal length (4.5-)5-6.5 mm, marcescent around base of forming pod but commonly shed before its maturity; petals glabrous yellow drying stramineous or whitish brown-veined, spatulate or obovate-cuneate of subequal length, 8.5-10 mm; androecium glabrous, the staminodes oblanceolate obtuse or emarginate, the 7 fertile members homomorphic except slightly accrescent toward Abaxial side of fl, the filaments 1.8-2.6 mm, the lunately narrowly lance-oblong anthers in profile 2.3-3.7 x 0.6-0.65 mm, just below apex slightly strangulated, dehiscent by a single subsymmetrically terminal pore; ovary densely white-pilo- sulous; style glabrous linear-filiform (1.8-)2-3.2 x 0.15-0.25 mm; ovules (16-) 18-26.

Pod erect sessile, in profile narrowly oblong or oblong-elliptic (2-) 2.3-3.5(-4) x 0.55-0.75 cm, at apex abruptly contracted into a symmetrically erect subulate beak, bicarinate by the sutures, strongly compressed laterally but turgescent and low-corrugate over seeds, the green early papery and fuscous valves paler along the sutural margins, densely minutely retrorse-pilosulous and more thinly hispid with antrorsely ascending straight setae up to (1-)1.2-1.7(-2) mm, downwardly dehiscent the length of both sutures, long persistent after seeds are shed; seeds turned with broader faces to the very narrow septa, stacked contiguously in 1 file along the laterally compressed cavity, in outline compressed- pyriform 3.2-3.8 x 2.2-2.8 mm, the faces raised in 3-4 obtuse folds radiating from the areole, the almost smooth testa dull pinkish or grayish-fawn, not rugulose-colliculate, the elliptic or round areole ±0.3 x 0.15-0.3 mm; n = 14.—Collections: 30.—Fig. 1 (petiolar nectary).