86 DOCTRINE OF CLEISTOGAMY. 
Upon this supposition the genus was never truly trimorphic, but 
only dimorphic. How is it possible to explain this case by the aid 
of Mr. Darwin’s doctrine ? Some people may say “ the species of 
r 
Bp 
then brought about by natural selection. It is o 
summer-flowering species would not produce closed flowers.” This 
The objection to this will be that the summer development of closed 
flowers is an adaptive modification. Granting this to be a valid 
objection, it becomes necessary to treat the hypothesis in the only 
way in which it is possible to refuse assent to the whole body of 
s philosophy, namely, by questioning its premises. The 
h 
universal experience; in fact it was only the other day that 
Mr. Hart in these pages (Journ. Bot. 1880, 
vegetation being of a perennial character. But further comment 
is useless, as the doctrine immediately collapses when questioned 
in way. 
I believe, then, that cleistogamy is caused by the physiological 
condition of great fertility wi t crossi 
species of Hranthemum, and many other instances. On the other 
hand, by adopting it, we escape from the dilemma of ascribing to 
an agency or agencies hostile to reproduction, the origin of a form 
. 
of it betraying so astonishing an amount of vitality. 
