98 The American Naturalist. [February, 
periods of particular flowers to particular species of insects, 
of families of plants to certain groups of insects, and the rel- 
ative positions of different groups. Under these circumstances, 
Mr. Clarke’s paper was read with particular interest, though it 
has not seemed to justify an abandonment of theoretical con- 
clusions previously held. 
The factors admitted by Mr. Clarke to have an influence in 
determining the blooming time of flowers are as follows: 
1. “The blooming period may sometimes vary from the 
general rule to better bring the flowers among the most favor- 
able conditions for cross-fertilization.” 
2. “Again, plants that are frontiersmen from the character- 
istic vegetation of a hotter clime may be expected in the hot- 
test of the seasons—e. g., the Cactaceae.” 
3. “There is an evident limitation of the flowering of our 
trees and shrubs to spring and earliest summer.” “The 
blossoming of so many trees, especially the Diclinae, in earliest 
spring, before leaf-budding, must evidently have at least partial 
connection with anemophilous cross-fertilization.” 
4. “Again, there is a determining function in the character 
of the flower’s habitat—the spring flowers seek largely the 
protection of the woodlands; marsh plants reach perfection 
mainly in latest spring and through the summer, though some, 
like Caltha, are early ; the aquatics of ponds and river glory 
in the summer sun; and the flowers of meadow and prairie 
and thicket margin luxuriate from midsummer to the end 
of autumn.” 
But the principal deductions of Mr. Clarke are these: “From 
early spring to late autumn there is a progression in the general 
character of the flower groups, from the lower to the higher—success- 
ive groups succeeding each other in time, parallel groups coming 
synchronously. And the later in order may be types of a higher 
character of development, or they may be specializations of 
a group whose normal forms belonged to an earlier season. 
In their blooming season, the more perfect succeed the more 
simple; the aberrant, the normal; the specialized, the g ral- 
ized.” | 
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