Senna villosa (Mill.) 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, collected in Campeche in 1730, ticketed successively by Houston and by Miller, BM! = BH Neg. 5166 = NY Neg. 162.—Desmodiocassia villosa (P. Miller) Britton & Rose, N. Amer. Fl. 23(4): 244. 1930.
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Synonyms
Cassia villosa Mill., Desmodiocassia villosa (Mill.) Britton & Rose, Cassia astroites Willd. ex, Cassia geniculata G.Don ex Ruiz & Pav., Cassia articulata Rose, Cassia villosa Mill., Cassia stellata M.E.Jones
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Description
Species Description - Amply leafy, sometimes arborescent shrubs at anthesis 1-4 m, densely scabrous-tomentulose throughout with thick-stalked gray or lutescent stellate hairs in profile 0.2-0.7(-1.1) mm tall, the thick-textured foliage bicolored, dull dark green above, paler beneath, the inflorescence of racemes either all axillary to cauline lvs or some late ones forming a small, shortly exserted subcorymbose panicle. Stipules erect, narrowly linear-attenuate or setiform 3.5-6 mm, caducous. Lvs 6-17 cm; petiole including swollen but not wrinkled pulvinus 1.5-3.5(-4.3) cm, at middle 0.8-1.8 mm diam, rounded dorsally, shallowly narrow-sulcate ventrally; rachis (1.3-)2.5-8 cm; glands (often eaten) between proximal and sometimes 1-2 next succeeding (but not the distal) pairs of lfts, stipitate or subsessile, in profile 1.3-3 mm tall, the stipe and commonly the head also stellate-pubescent, the latter either slenderly or squatly ovoid, acute or obtuse 0.4-1.2(-1.6) mm diam; pulvinules 1-2.5 mm; lfts (2-)3-5, of most lvs either 3 or 4 pairs, accrescent distally, the distal pair lance- or elliptic-acuminate, ovate-elliptic, ovate-acuminate or obliquely ovate and deltately subacute (2-)2.7-8 x (1.8-) 1.2-2.7 cm, 2.2-3.8 times as long as wide, at oblique base cordate to rounded on proximal and rounded to cuneate on distal side, the margin revolute, the midrib and (5-)6-9(-10) pairs of incurved-ascending camptodrome secondary nerves immersed above, finely prominent beneath, the tertiary venulation imperceptible. Peduncles 1-3.5(-5) cm; racemes densely 5-25-fld, the axis somewhat elongating, becoming 3-30 mm; bracts subulate-filiform 2-5 mm caducous; pedicels slender 6-13 mm; fl-buds oblong-ellipsoid obtuse, nodding when young; sepals submembranous, densely stellate dorsally except where interior in vernation, of nearly equal length, elliptic-oblong 5-8 mm; petals pale yellow fading whitish brown-veined, glabrous dorsally, subhomomorphic except the 2 abaxial a trifle longer, all obovate-cuneate obtuse or subemarginate, the longest 7.5-10 x 4-6 mm; androecium glabrous or the filaments remotely stellate, functionally 7-merous, the filaments alternately a little longer (oppositisepalous) and shorter 1.6-2.7 mm, the linear-lanceolate anthers brown when dry, not much differentiated, those of 4 median stamens nearly straight 3.1-4 mm truncate, those of 3 abaxial ones a trifle longer, 3.8-5 mm, and more incurved, constricted 0.2-0.4 mm below the somewhat oblique 1-pored orifice; ovary densely stellate-tomentulose; style glabrous, gently incurved 2-2.5 mm, at attenuate apex ±0.2 mm diam; ovules (8-)10-18. Pod obliquely pendulous, the stipe 2-4 mm, the body in profile undulately moniliform 6-10 x 0.4-0.55 cm, laterally compressed, slenderly carinate by the sutures, constricted between the seeds, the isthmi 1.5-4 mm wide, the seed-locules 5-8 mm long, when ripe separated in the form of achenes, the firmly papery green, brunnescent valves densely stellate, elevated over each seed as a narrow ridge oriented lengthwise to the pod; seeds basipetally vertical to the long axis of pod, obovoid compressed parallel to valves, 3.7-4.5 x 2.6-3.1 mm, the testa fawn- or chocolate-brown smooth but not or scarcely lustrous, crackled, the subcentric areole oval (0.7-)0.8-1.5 x (0.5-)0.6-l mm.—Collections: 44.— Fig. 9 (petiolar nectary), 14 (pod, seed).
Distribution and Ecology - Scrub thickets and brushy canyon slopes, 10-1600(-1860) m, in continental Mexico (and presumably Bahamas) often calciphile, local, s.-e. Mexico from centr. Veracruz to Yucatan, the headwaters of Rio Grande in Chiapas, s.-e. and centr. Oaxaca, and Puebla, in the two latter states entering the Pacific drainage; remotely disjunct in the foothills of the Cape mountains in s. peninsular Baja California; and (perhaps naturalized) on New Providence I. in the Bahamas.— Fl. in continental Mexico VIII-I; on the Cape V-X.
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Discussion
The singular stellate hairs which clothe the stems, foliage, inflorescence and pod of S. villosa are composed of a thickened, often yellowish or rufescent stalk bearing on its summit a tuft of fine radiating and ascending whitish filaments. The whole trichome suggests a diminutive sea anemone and is unique in Senna to this one species. The populations of S. villosa on the Cape mountains of Baja California differ from those of continental Mexico in the less obviously acuminate leaflets and somewhat less pronounced constriction of the pod valves between seeds, the isthmi being 3-4 (not 1.5-3) mm wide. These slight differences, expectable in the circumstances, are insufficient for taxonomic recognition.
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Distribution
Veracruz Mexico North America| Yucatán Mexico North America| Chiapas Mexico North America| Oaxaca Mexico North America| Puebla Mexico North America| Baja California Mexico North America| New Providence Bahamas South America|