ECOLOGY OF FLOWERS 355 
characteristics of such flowers are the inconspicuous char- 
acter of their perianth, which is usually green or greenish, 
the absence of odor and of nectar, the regularity of the 
corolla, and the appearance of the flowers before the leaves 
or their occurrence on stalks raised above the leaves. 
Pollen is, in the case of a few aquatic plants, carried 
from flower to flower by the water on which it floats. 
425. Insect-Pollinated Flowers. — Most plants which 
require cross-pollination depend upon insects as pollen- 
carriers,! and it may be stated as a general fact that the 
showy colors and markings of flowers and their odors all 
serve as so many advertisements of the nectar (commonly 
but wrongly called honey) or of the nourishing pollen 
which the flower has to offer to insect visitors. 
Many insects depend mainly or wholly upon the nectar 
and the pollen of flowers for their food. Such insects 
usually visit during any given trip only one kind of flower, 
and therefore carry but one kind of pollen. Going straight 
from one flower to another with this, they evidently waste 
far less pollen than the wind or water must waste. It is 
therefore clearly advantageous to flowers to develop such 
adaptations as fit them to attract insect visitors, and to 
give pollen to the latter and receive it from them. 
426. Pollen-Carrying Apparatus of Insects.2—- Ants and 
some beetles which visit flowers have smooth bodies, to 
which little pollen adheres, so that their visits are often of 
slight value to the flower, but many beetles, all butterflies 
and moths, and most bees have bodies roughened with 
scales or hairs which hold a good deal of pollen entangled. 
1 A few are pollinated by snails; many more by humming-birds and other 
birds. 2 See Miiller’s Fertilization of Flowers, Part II. 
