Senna arida (Rose) 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
"Type [US] no. 453267, collected by J. N. Rose and Jos. H. Painter, near Higuerillas, Queretaro, August 23, 1905 (no. 9778)." Holotypus, US! Earleocassia arida (Rose) Britton ex Britton & Rose, N. Amer. Fl. 23(4): 249. 1930.
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Synonyms
Earleocassia arida (Rose) Britton
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Description
Species Description - Closely related to S. argentea and differing in the following respects: setose pubescence of stems and lf-stalks shorter or sparser or both, the longest trichomes 0.8-1.5(-3.5) mm; lfts mostly 2 or 3, occasionally 4 pairs; peduncles up to 8.5 cm; pedicels 8-20 mm; filaments 2.3-3 mm, the anthers gently incurved (1.8-)2-2.8 x 0.5-0.7 mm; style 0.6-1.2 x 0.3-0.5 mm, 2-3 times as long as apical diam; pod linear-oblong 3-4 x 0.5-0.6 cm, the long vesture of the valves composed of ascending setae up to 1-1.4 mm; ovules 30-36; seeds more crowded than those of S. argentea, hence disposed in 2 interdigitating ranks.—Collections: 9.
Distribution and Ecology - Matorral, disturbed oakwoods and mesquite-grassland, 1600-2000 m, in scattered stations around the s. edge of the Mexican Plateau in s.-w. Zacatecas (San Juan Capistrano), Guanajuato, Queretaro (Higuerillas, Queretaro) and Hidalgo (Tasquillo, Orizabita), and disjunctly in n.-w. Oaxaca (distr. Teposcolula and Huajuapan) and immediately adj. Puebla (Caltepec).—Fl. V-VIII.
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Discussion
Senna arida has been collected seldom and its full dispersal and range of morphological variation can only be guessed at. For the present it appears very close to S. argentea, of which it has the habit and short thickened style, but it differs in smaller anthers and shorter pod with seeds consequently crowded and displaced into two rows. The collections from the Oaxaca-Puebla border seem essentially identical to those from the southern edge of the Mexican Plateau. One plant from Queretaro (Rose 11184, ex parte, NY) and another from Guanajuato (Kenoyer 2285, A, described by the collector as a shrub) have stems hispid with lustrous setae up to 2.5-3.5 mm long, suggestive of S. argentea, but with the short pod of S. arida. The amply documented instability in vesture of Senna generally and ser. Brachycarpae in particular induces us to make light of this visually arresting variation.
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Distribution
Zacatecas Mexico North America| Guanajuato Mexico North America| Querétaro Mexico North America| Oaxaca Mexico North America| Puebla Mexico North America|