Senna wislizeni var. villosa

Title

Senna wislizeni var. villosa

Author(s)

Howard S. Irwin, Rupert C. Barneby

Scientific Name

Senna wislizeni var. villosa (Britton) H.S.Irwin & Barneby

Description

193d. Senna wislizeni (A. Gray) var. villosa (Britton & Rose) Irwin & Barneby, Phytologia 44(7): 500. 1979. Palmerocassia villosa Britton ex Britton & Rose, N. Amer. Fl. 23(4): 254. 1930.-"Mapimi, Durango, October 21-23. 1898, E. Palmer 518."-Holotypus, NY! = NY Neg. 9393; isotypi, GH, US!-Cassia wislizeni var. villosa (Britton & Rose) Irwin & Barneby, Sida 6(1): 16. 1975.

Like var. wislizeni except for the pilosulous vesture; primary lvs 10-25 mm, with 2 or 3 pairs of lfts, the largest 3-8 mm; body of pod 7.5-16 x 0.6-0.8 cm, 24-30-ovulate, otherwise as in var. wislizeni.-Collections: 5.

Larrea scrub and matorral, in canyons and foothills of desert mountains, strongly calci (or gypso)-phile, 1250-1860 m, local around the s.-w. periphery of Mapimi Depression and the lower Nazas valley in far s.-w. Coahuila and adjacent Durango.-Fl. VI-IX.

This variety is weakly distinguished from var. wislizeni by its loose vesture but so definitely segregated geographically that we think it useful to recognize it formally. The leaflets are on the average fewer by one pair than in var. wislizeni and lead on to the related S. monozyx, its vicariant neighbor in south-central Coahuila, in which all leaves are bifoliolate.