120 
Floral Evolution, 
(a) . The reduction of the stamens to a number less than that 
of the corolla segments, following upon zygomorphy 
or asymmetry, e.g., Tubiflorse, Aggregate. 
(b) . The progressive reduction of the calyx, to a pappus, or to 
zero. 
(c) . The reduction of the carpels to two (Bicarpellatse and 
Asterales), the loculi to one, and the ovules to one 
(Asterales). 
The tendency to progressive adaptation to insect-visits is 
reflected in:— 
(a) . The general introduction to zygomorphy, in Tubiflorse on 
the one hand, and in Aggregate and Campanulatae 
on the other. Our two “types” of zygomorphy are 
thus both represented. 
( b ) . The “ pollen-presentation ” mechanism, a general feature 
of the Campanulatae. 
With these general considerations as an introduction, we 
shall proceed, in future chapters, to consider the sympetalous cohorts 
in detail, and endeavour at the same time to apply the principles of 
floral evolution which have been enunciated. 
