THE GEOGRAPHICAL DISTRIBUTION OF THE GENUS SPHAERANTHUS

Abstract

I N a previous paperl on the genus Spfiaeranthus Vaill. (Compositae) I was mainly dealing with its classification and possible phylogenetic evolution. I now take the opportunity of pointing out some outstanding features in its geographical distribution, and bring forward further evidence regarding the undoubted great affinity between certain East African and Indian species. The genus Sphaeranihus is chiefly confined to the tropics of the old world, its northern and southern limits corresponding almost with the tropic of Cancer and the tropic of Capricorn respectively. Only the four most widely spread and best known species slightly extend beyond the northern boundary: S. suaveolens DC. (Oocephalae), and S. africanus Linn., S. indicus Linn., S. senegalensis DC. (all three Sphaerocephalae). In addition, S. strobuliferus Boiss. et Noe (Oocephalae) seems to be endemic in Persia as specimens are as yet only recorded from that region. As to the southern limit given above, S. peduncularis DC. is only known by specimens from Natal, and S. incisus Robyns is mainly distributed in the Transvaal and Swaziland, but also occurs as an outlier in tropical South Angola. These two closely allied South African species belonging to the section Oocephalae, and differing mainly by the deeply incised wings of the branches and the shorter peduncles of S. incisus, have also a similar geographical distribution. The western limit of the genus extends as far as the Cape Verde Peninsula, but only one species, S. senegalensis, has nowadays been met with in this far West African region, no other species spreading more westward than Northern Nigeria. The eastern limit of distribution is to be found in the Philippines (Luzon) and North Australia, but again only two species are recorded from these regions, and all the others are confined to the Asiatic Continent.