A New Subspecies of Indigofera patula Baker (Leguminosae-Papilionoideae) and a New Record for the Species in West Africa

Abstract

Two recent collections of a previously unknown member of the taxonomically difficult and speciose Indigofera section Viscosae Rydb. (Schrire 1995) have been made from the Mt Oku area in the North West Province of Cameroon. They were gathered during a botanical inventory conducted jointly by the National Herbarium of Cameroon and the Royal Botanic Gardens, Kew (Cheek et al. 1997). The specimens were initially identified as being allied to Indigofera atriceps Hook. f. (but lacking the characteristic blackish hairs of that species) and Indigofera mimosoides Baker, both of which are recorded for Cameroon. Closer examination, however, revealed that these collections are apparently closest to the East and South-Central African Indigofera mimosoides Baker var. viscidior J. B. Gillett, which as a result of revisionary work by the first author for the Flora Zambesiaca account of Indigofera, has been placed in synonomy under Indigofera patula Baker. The latter differs from I. mimosoides in being usually a perennial herb or suffrutex (not an annual herb), with shorter, more even and numerous, conspicuously blackish gland-tipped hairs 0.1 1(3) mm long (vs. longer, more slender, less even and fewer glandular hairs to 4(5) mm long, not or minutely gland-tipped); leaflets with the margins and often the midrib beneath fringed with gland-tipped hairs (vs. leaflet margins of juvenile leaflets only with glandular hairs) and larger flowers with stamens 4 7 mm long and the style 3.5 4.5 mm long, bent to erect ? in the distal third (vs. stamens (2.5 -)3 4.5 mm long and the style 2.8 3.5 mm long, bent to erect ? in the middle). Mt Oku (3011 m) is the second highest mountain in Cameroon after Mt Cameroon (4095 m) and is part of the Bamenda Highlands, a chain of mountains with many peaks above 2000 m. The Bamenda Highlands are densely populated and intensively cultivated and grazed. The largest fragments of natural vegetation remaining in the Bamenda Highlands are believed to be those at Mt Oku which is protected by the Kilum-Ijim Projects managed by BirdLife International. Montane