Origin and Development of the Composite ?. 19 
are discussed below (Sect. D). The Helichryseae are clearly South 
African in origin, as are several sub-tribes (see Fig. 33). 
The only other wide spread sub-tribes are, (a) the Plucheinae, 
which, with their chief centre in tropical Africa, have subsidiary 
centres in tropical Asia and Australia, and also extend into all 
the American regions, (6) the Filagininae, which, although rather 
diffuse and extending to Mexico, have a distinct centre in the 
Mediterranean region. 
The Inulinae, although fairly widespread in the Old World, are 
markedly Mediterranean in origin, as is shown by maps of the 
species of the widespread genera, especially Inula and Pulicaria. 
Another point of interest is the centre of the Buphthalminae at the 
eastern end of the Mediterranean region. 
Cynarece. The centre of origin, as indicated by the coincidence 
of the region of concentration of local species with the region of 
the overlapping of the areas of the widespread species, is nowhere 
more clearly indicated than in Centaurea (Fig. 34). The centre for 
all the sub-tribes is at the eastern end of the Mediterranean region, 
and the same type of map is shown by all the wide spread genera 
of the Cynareae. The paths of migration are the more arid regions 
along the mountain ranges, but this is shown better by Cnicus and 
Echinops than by Centaurea. Only the last genus extends to Chili 
but Cnicus extends to Mexico and Saussurea to the U.S.A. 
Mutisieae. There is in this tribe no genus common to the 
Old World and America with the exception of the South American 
genus Trichocline, which has one species in Australia. An analysis 
of all the genera in each sub-tribe shows that the chief centre for 
each is in South America (Fig. 35). The Nassauviinae and the 
Barnadesiinae are confined to America, but the other three sub¬ 
tribes have some genera in Africa. The two geographical groups 
of genera are illustrated by two of their most wide spread 
members, Trixis and Gerbera. Trixis angustifolia extends north to 
California and Arizona, while Gerbera Anandria extends to north 
Siberia. The paths of migration are the same as in Senecio, but 
a gap exists between Siberia and California. The Nassauviinae 
show a marked concentration of both species and genera in Chili; 
although the local species of Trixis are chiefly Mexican, there are 
a number of local species in Brazil, and the commonest species, 
T. divaricata, is South American. 
Vernoniece. The type of distribution here is quite a simple 
one. The centre of concentration is in Brazil, and there is an 
