Origin and Development of the Compositee. 217 
section of Senecio, which approaches the Eupatorieae, particularly 
in the characters of the style. 
The place of origin for all three sub-tribes of the Eupatorieae 
is clearly the Mexican region. 
In discussing the age of the Eupatorieae Bentham ( loc. cit.) 
showed more than his usua lremarkable perspicacity. He considered 
that the Eupatorieae “ may he regarded as one large and natural 
essentially American group or genus in an extended sense of the 
term ; ” that they “ must, therefore, either not he so ancient as some 
other groups of the Compositae, or some other reason must have 
interfered with their early dispersion.” Discussing the truncate 
anther-tips of the Piqueriinae he says, "This remarkable deviation 
from the almost absolute uniformity of Compositae is probably, 
therefore, of West American origin, and not ancient enough to have 
spread into other continents now severed from America/’ 
The fossil evidence of the early history of the Eupatorieae is 
interesting. The species of Eupatorium which now occupies the 
greatest area is identified in the fossil condition in Interglacial times, 
and other species are described from the upper and middle 
Pliocene. Considering these points and those indicated by Benthamj 
the date of origin of Eupatorium must be not later than the lower 
Pliocene. Taking into account the comparative development of 
the Eupatorieae and the Arctotideae (which is assigned above to the 
lower Pliocene) and the fact that Eupatorium had apparently 
arrived in Europe as early as the middle Pliocene, the most 
probable date of origin for the genus and tribe seems to be the 
middle Miocene. 
The Eupatorieae and Vernonieae would on this hypothesis have 
arisen more or less at the same time. This would account for the 
similarity in sub-tribal and generic differentiation in these two 
tribes, as well as for the similarity in their geographical distri¬ 
bution (cp. Figs. 36-37). 
Helianthece. Throughout the preceding chapters no reason 
has appeared for making any change in-the phylesis suggested for 
the Heliantheae in Fig. 7. A more detailed analysis of the genera, 
however, suggests certain modifications. The Verbesininae is 
clearly the primitive sub-tribe and Spilanthes is the most probable 
primitive genus for the sub-tribe (see Chap. X, C). In connection 
with the setiform aristae of this genus it is interesting to note that 
Blake (159), discussing the few-membered, paleaceous pappus of 
Hymenostephium , says that it “ is certainly not to be looked upon 
