Entry From
Flora of Tropical East Africa, Part Part 3, page 547, (2005) Author: H. Beentje, C. Jeffrey & D.J.N. Hind
Notes
: The structure of the capitula is ideal for the efficient dispersal of mature achenes. The hairs on the outer surface of the corolla become matted together so that, at maturity, the whole mass lifts away together, aided by the outward movement of the receptacle. This exposes the pappus pegs with their sticky tips to contact with animals and thus they are dispersed. Because of this, the genus is widespread and characterised by considerable variation which has in turn led to much confusion in its taxonomy. The group is in desperate need of revision, the last comprehensive work being that of de Candolle (1836). Since that time, a number of conflicting views have been published in the literature. In F.T.A., Oliver placed A. mauritianum, A. caffrum and A. perrotteti under the pantropic A. viscosum of J.R. & G. Forster. F.W.T.A. ed. 1 on the other hand treated A. mauritianum, A. perrotteti and A. viscosum as being the three species represented in the area, with A. caffrum appearing in the synonomy of A. viscosum Forst. This view was revised for F.W.T.A. ed. 2 where A. caffrum was given as an accepted species, with A. viscosum Forst. in synonomy. Lisowski in Asteraceae d’Afrique Centrale also recognised 3 species, namely A. mauritianum, A. perrotteti and A. caffrum. He considered that A. viscosum had been misused by authors for A. perrottetii and A. caffrum, but declined to treat A. viscosum sensu J.R. Forst. & G. Forst. As a result of my survey, I have chosen an alternative explanation. After inspection of A. viscosum J.R. Forst. & G. Forst. from other paleotropical regions, I have relegated A. perrottetii to the synonomy of A. viscosum, a view supported by King & Robinson (1987). A. mauritianum is easily distinguished by its glabrous achenes (other African taxa have tuberculate achenes), and is retained. A. caffrum differs from A. viscosum by size and number of capitula and by number of corolla lobes and anthers, and by sessile, lanceolate leaves. It is endemic to Africa, whereas A. viscosum has pantropic distibution.