246 EVOLUTION OF PLANTS 
time, by further modifications of their descendants, 
other adaptations for cross-pollination would arise. 
There are many genera, especially among the lower 
Dicotyledons, which exhibit in a most interesting way 
all gradations between inconspicuous self-pollinated 
flowers, and showy ones dependent upon insects. This 
is shown, for example, 
in the genus Ranun- 
culus, which includes ' 
the various species of 
buttercup. The in- 
conspicuous #. abor- 
tivus is entirely in- 
dependent of insect 
aid, while such showy 
species as R. acris or 
R. Californicus are 
visited freely by in- 
sects, although they 
Fic. 55.—A, flower of Anemone coronaria 
the petals absent, but replaced by the Te probably not en- 
showy sepals, s; B, inflorescence of the i 
dogwood (Cornus * florida), the incon- tirely dependent i ee 
spicuous flowers, fl, surrounded by four them to insure fertili- 
showy bracts, b; C, the “calla-lily” fi ae A 
(Richardia), with the central spike of zation. Similar vari- 
wee ona aes UY the Jar ation is found in the 
genus Geranium. 
In the simplest of these “ entomophilous” or insect- 
fertilized flowers, such as the buttercup or anemone 
(Fig. 55, A), the flower is wide open, with the entirely 
separate parts arranged radially, and often indefinite 
in number. We find in such generalized flowers that 
the variety of insects visiting them is large, and they 
are seldom incapable of self-pollination in case insect 
