KINDS OF POLLINATION 47 
depend upon the wind for pollination. The wind is also an 
important agent in the pollination of Corn and aids some in 
orchard pollination. Plants having showy flowers depend upon 
insects for pollination and it is among these plants that attractive 
colors, secretions of nectar, and various structural arrangements, 
which are interpreted as adaptations to secure pollination, occur. 
The pollination of Fruit trees, Clovers, and Alfalfa is done chiefly 
by insects. (Fig. 56.) In experimental work, such as crossing 
Fic. 56. — Bumble bee pollinating Red Clover. 
Tomatoes, Corn, and Fruit trees, man himself often does the 
pollinating so as to have it under control. 
Kinds of Pollination.— On the basis of the relation of the 
stamen furnishing the pollen to the pistil pollinated, there can 
be different kinds of pollination. The transfer of pollen from 
the stamen to the pistil of the same flower is self-pollination, 
while the transfer to the pistil of another flower is cross-pollina- 
tion. Various relationships may occur in pollination. Thus the 
