218 





Fig. 221. Flower of Canna 
Below is the ovary surmounted by 
three small sepals, within which are 
three narrow petals. The conspicuous 
parts are the stamens, the central one 
of which bears an anther on the mar- 
gin to the left. In the center of the 
flower is the stigma. (x 2) 

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Fig.222. Flower head of bachelor’s 
button (Gomphrena globosa) 
The flowersare small, and each is sur- 
rounded by two conspicuous white or 
brightly colored specialized leaves or 
bracts. (x 1) 
A TEXTBOOK OF GENERAL BOTANY 
Insect-pollination. Insects are 
attracted to flowers by their odor, 
by their conspicuousness, or by 
both odor and conspicuousness, 
and visit them for the purpose 
of collecting nectar and pollen, 
which serve them as food. While 
visiting a flower the body of 
an insect becomes dusted with 
pollen, which may subsequently 
be caught on the stigma of an- 
other flower visited. 
Nectar is a sweet liquid that 
is secreted by glands which may 
be on the torus (Fig. 203) or on 
the petals. Conspicuous cavities 
in the petals frequently contain 
nectar glands. Bees use nectar 
in making honey. 
Many flowers that do not se- 
crete nectar produce large quan- 
tities of pollen, which serves as 
food for insects. Although the 
insects may use a considerable 
part of the pollen, nevertheless 
some of it sticks to their bodies 
and is carried to the stigmas of 
other flowers. 
Insect-pollinated species fre- 
quently have pollen which either 
is sticky or is furnished with 
humerous projections which help 
make the pollen adhere to the 
body of an insect, while the 
bodies of the pollinating insects are usually hairy. When 
the stigma of a flower is mature, it has a sticky surface to 
