POLLINATION AND FERTILIZATION 139 
3. Flowers with conspicuous perianth, often with odor, 
often with nectar, usually with moist or sticky pollen, with 
knob-like or club-shaped stigmas. 
«A good example of 1 is the flower of the peppergrass (Lepid- 
vom); of 2, the flowers of the grasses; of 8, the showy garden 
flowers, such as lilies, pinks, and roses. 
131. Modes of pollen-carrying. Each of the 
three groups just described corresponds to a 
different mode of transference of pollen from 
anther to stigma. 
The flowers of 1 either themselves carry 
pollen from the stamens to the stigma of the 
same flower (for example, by the curving 
inward of the stamens as the flower matures) 
or have it carried from stamens to pistil within 
the flower by insects which visit the flower, 
usually in search of pollen. Such flowers are 
said to be se/f-pollinated. 
In the flowers of 2 the pollen is carried, 
preferably from a flower on one plant to a 
flower on another plant, by aid of the wind 
or, in the case of a few aquatic plants, by 
water. Such flowers are said to be wind- 
pollinated or water- pollinated. Fic. 121. Pistil of 
In the flowers of 3 the pollen is carried, timothy,withfeath- 
i ery stigmas 
preferably from a flower on one plant to e 
a flower on another plant, usually by in- 
sects that visit the flowers in order to 
secure food.! Such flowers are said to be inseet-pollinated. 
132. Self-pollination and cross-pollination. There is a very 
great physiological difference between self-pollination (1) and 
cross-pollination (2 and 8). In self-pollination the male cell 
and the egg nucleus with which it unites originate in the same 
flower ; in cross-pollination they originate in different flowers, 
preferably from flowers borne on different plants. 
sti, stigmas. Mag- 
nified about 20 times 
1 Sometimes the pollen is carried by birds, bats, snails, or other animals. 
