T H E 
NEW PHYTOIiOGIST. 
Vol. X, Nos 7 & 8. 
July & Oct., 19 i i. 
[Published November 20th.] 
FLORAL EVOLUTION: WITH PARTICULAR REFERENCE 
TO THE SYMPETALOUS DICOTYLEDONS. 
By H. F. Wernham. 
IV. Tetracyclid/£ : Part I. Contorts. 
JHE Pentacyclidae, we have found, reflect the earliest evolu¬ 
tionary “ efforts” in the direction of sympetaly, and so hear 
many marks of their archichlamydeous origin, particularly in regard 
to the numbers of the parts and cohesion of the petals. In the 
Tetracyclidse, on the other hand, the stamens alternate with, and 
never exceed in number, the corolla segments; the gynaecium is in 
the majority of the species bicarpellary; and the petals are almost 
invariably united to form a tube. In other words, the primary 
principle of economy has reached its highest expression, and 
sympetaly, the fundamental step in the direction of adaptation to 
insect-visitors, is established practically without exception; we 
anticipate, therefore, that the guiding principle of evolutionary 
progress which we shall observe among the Tetracyclidae will be 
further adaptation to insect-visits. This adaptation may take a very 
special and complex form, as in Contortae (Asclepiadaceae); or it 
may be of such extensive occurrence as to represent a general 
evolutionary tendency, as in the case of the zygomorphy of the 
Tubiflorse and the aggregate inflorescence of the higher Campanu- 
latse. The latter, moreover, display a special advance in their so- 
called “ pollen-presentation ” mechanism. 
The fundamental lines of advance in the direction of adaptation 
to insect-visitors are associated with certain tendencies which we 
have already referred to as secondary economy tendencies. Thus, 
sympetaly becomes associated with epipetaly, as we have seen 
