POLLINATION AND FERTILIZATION 111 
is taken by insects for food, the rest being used for 
pollination. The Poppy is a pollen flower. 
It may be observed here that insect-pollinated flowers 
have an advantage over those depending on the wind, 
inasmuch as their pollen is not wasted, they do not 
have to produce nearly as much of it, and they can 
have quite small stigmas. On the other hand, they 
have to produce a corolla, honey and scent, and should 
there be a scarcity of insects they run the risk of not 
getting pollinated at all. 
Hydrophilous (water-pollinated) flowers are rare and 
only occur in a few aquatic plants. 
77. Cross=Pollination.—It has been found that cross- 
fertilization produces on the whole stronger and healthier 
offsprings. Darwin, in his book ‘‘ Cross and Self Fertiliz- 
ation of Plants” gives an account of experiments which 
he carried out for a number of years, and he found that, 
in general, the offspring of cross-fertilized plants were 
superior in height, weight, and fertility to the offspring 
of self-fertilized plants. This being so, we should expect 
to find in the higher plants devices for favouring or 
ensuring cross-poilination. This is the case. 
78. Contrivances and Conditions Favouring Cross- 
Pollination.-—(@) Diclinism.—The simplest method of 
ensuring cross-pollination is to have stamens and pistil 
on different flowers (diclinism). If the flowers are on 
separate plants, they are known as DIOECIOUS, e.g. 
Willow (Salix), if, on the same plant, they are Mon- 
OECIOUS, e.g. Ricinus, Cucumis Begonia and Pumpkin 
(fig. 60). 
(b) Dichogamy.—Another method of avoiding self- 
