21 
illustrated by the South African Flora . 
Grahamstown, and is one of the first arrivals under the pioneer thorn-trees 
in the thorn- veld ( 9 ). R. parvifolia (listed by Medley Wood) is hardly 
distinct from R. rudis. Similar relationships may be observed between 
Gardenia Thunbergia , a very widespread tropical species, and other South 
African species of Thunbergia (cf. Stapf and Hutchinson, 34 ). The genera 
Tricalysia , Plectronia , Vangueria , and Pavetta also illustrate our general 
principles. 
Pavetta caffra is chiefly a coast-belt species. P. Cooperi is a very closely 
allied species, and is only found in the midlands. The genus Plectronia 
extends from Natal to the Cape Peninsula, the species being light-demanding 
pioneers. All the species come very close together, and may have been 
derived from the breaking up of a single widespread ancestral type. 
Compositae. 
Though this great family is full of interest in its distributional aspects, 
as has been very fully demonstrated by the detailed work of Small ( 32 ), 
it must also be passed over with very brief reference. Schonland ( 30 ) finds 
several more or less well-defined groups of genera according to their 
distribution in South Africa, viz. over 40 genera with general distribution, 
about 20 genera radiating from the Transvaal and Natal along the southern 
coast, over 40 genera mainly in the south-west, a small group chiefly 
central, and a few genera with very restricted distribution. There are also 
a very large number of species with extremely restricted distribution, as 
is to be expected in the family since it is a feature which it exhibits all 
over the world. On the other hand, many species are generally distributed, 
and many more have a wide range over one or more of the distinct climatic 
areas. Examples of our general principles may be found in the genera 
Vernonia , Nidorella , Brachylaena , Sphenogyne, Pentzia , Co tula , Athanasia , 
Helichrysum^Metalasia , Stoebe, Othonna , Senecio , Euryops , Dimorphotheca y 
Osteospermum y Berkheya , and many others. 
Migration of widespread ancestral types has very clearly, in a great 
many cases, perhaps in the majority, been along the mountain ranges. 
Ericaceae. 
Schonland remarks ( 29 ) that the distribution of the Ericaceae defies at 
present a satisfactory explanation. * Their prevalence in South-West Africa 
and the prevalence of Epacridaceae in Australia cannot be used as evidence 
that these two orders originated in the southern hemisphere from common 
ancestors (compare Drude in Engler-Prantl, iv. 1, 1897, 29 ).’ We shall 
return to this point later. 
There are 17 genera of Ericaceae with 146 species all endemic in the 
south-western region of Macchia. The genus Ericinella has one species 
at Graaff Reinet, one at Queenstown, and 3 or 4 in tropical Africa or 
Madagascar. The genus Phillipia has 4 species at the Cape, a few in 
tropical Africa, and 20 to 30 in the Mascarene Islands. The great genus 
