Senna silvestris subsp. bifaria

Title

Senna silvestris subsp. bifaria

Authors

Howard S. Irwin, Rupert C. Barneby

Scientific Name

Senna silvestris var. bifaria H.S.Irwin & Barneby

Description

3/II. Senna silvestris (Vellozo) subsp, bifaria Irwin & Barneby, subsp, nov., a subsp, silvestri imprimis foliolis dorso alte subalveolatim reticulato- venulosis, pube magis copiosa laxiori patula etiam per foliolorum faciem ventralem sparsa abstans.—Typus infra sub var. bifaria indicate.

Cassia silvestris sensu Bentham, 1870, p. 125; 1871, p. 549; non C. silvestris Vellozo, sens. str.

The subsp, bifaria, as defined in our key above, is equivalent to Bentham’s Cassia silvestris, differing from genuine S. silvestris in the close subalveolate reticulation of the leaflets’ dorsal face and in the more copious pubescence of incumbent or curly hairs that extends, even though sometimes inconspicuously, over the leaflets’ ventral face. The leaflets of subsp, bifaria tend to be slightly fewer and more broadly rounded at base than those of subsp, silvestris, but are far from consistently so. The petals of subsp, bifaria are often streaked at base with red, not uniformly yellow as those of subsp, silvestris, but the red pigment is easily lost in drying, and we have no systematic information on this point. The thick texture and coarse venation of the pods of var. bifaria and var. unifaria might furnish specific criteria supporting Bentham’s separation of two independent species in this group, but subsp, bifaria var. velutina, described below, combines the characteristic foliage of its subspecies with the pod of subsp, silvestris. The present subspecies consists of three varieties, differing principally in width and texture of the pod and in alignment of the seeds within it. Each variety is neatly vicariant in range.