Origin and Development of the Composite 233 
Helenieae were originated. In all four cases a tendency to lateral 
fusion of the pappus hairs was present, and similar climatic and 
other ecological conditions are indicated by other data. 
About the same time the tendency to reduction in the number 
of fruits, which is seen in the Melampodiutn line, became effective 
in the ancestral plexus of that genus and the one-flowered capitulum 
of Lagascea was developed in the Mexican region. In the northern 
sub-arctic regions of Asia the cold and other adverse conditions, 
including the short vegetative season, induced some of the 
Senecioninae to assume the geophilous habit of Petasites. 
Pliocene Period. 
Events in the lower Pliocene occurred chiefly in the Old World 
and notably in South Africa. The above-mentioned origin of the 
Metalasia, Relhnnia and Berkheya groups and of the Tarchonanthinae 
took place then. In addition those Senecioninae in South Africa 
which were fortunate enough to have occupied the moist valleys 
found a reduction in fruit-number possible and the disc florets 
became sterile. As usual such conditions resulted in the reduction 
or complete suppression of the pappus, which was replaced in this 
case by bent apical beaks, tuberculations, and other structures 
suitable for animal dispersal. In this way the Calenduleae were 
developed. 
Differentiation in the Mediterranean region was active chiefly 
in the Cynareae as far as sub-tribes were concerned; the two groups 
of the Carlininae and the Echinopsidinae with aggregated, few- 
flowered capitula are probably the result of the working out to 
the furthest limits of efficiency of the two tendencies, aggregation 
and reduction. A large development of the Carduinae is also 
suggested. 
Reduction and aggregation were nearing the limits of efficiency 
in other tribes also and similar “ end-products ” can be traced in 
other geographical regions. Within the limits of efficiency but 
showing reduction came the Adenostylinae via Brickellia, but in the 
same Enpatorium plexus the limits were passed in the Piqueriinae 
which, originating in Adenostenuna , remained as a consequence of 
their inefficiency a small, restricted group. These were Brazilian 
events and in the same region a parallel development occurred in 
the Vernonieae, where the few-flowered, aggregated capitula of the 
Lychnophorinae were developed in Elephantopus. Another very 
similar development occurred in the origin of the reduced, dioecious 
and geographically restricted Petrobiinae in the Chilian region. 
