8o CROSS-POLLINATION 



(vi.) Usually a large amount of pollen is produced. 



These characters serve to illustrate the general peculiarities 

 of wind -pollinated flowers. The wind-pollinated flowers of 

 the Pine differ in that the pollen is blown on to the open 

 carpels, but here the open crevices of the carpellary cone 

 must be regarded as exposing the large surface to receive 

 the poljen. 



Cross-pollination by the agency of insects — Insect-pol- 

 linated flowers. — The Buttercup, Wallflower, Poppy, Pea, and 

 Hyacinth all possess flowers which are cross -pollinated by 

 the agency of , insects. They serve to illustrate the general 

 features of insect-poHinated flowers. 



(i.) They are brightly coloured or scented. 



(ii.) They usually possess nectaries, for the sake of whose 

 honey insects visit them ; occasionally {e.g. Poppy, Potato) in- 

 sect-pollinated flowers do not manufacture honey, but supply 

 their insect-visitors with food in the form of pollen. 



(iii.) The pollen-grains, in place of being powdery, are usually 

 sticky, so that they adhere to the bodies of insects. 



(iv.) There is a certain correspondence between the positions 

 of the anthers and the stigmas of the flowers. 



(v.) The stigma is not feathery or pencil-like, but, as a rule, 

 is relatively small. 



These general statements are liable to exceptions ; some 

 insect-pollinated flowers are inconspicuous, and, so far as we 

 can smell, are also scentless {e.g. Virginia Creeper). Insect- 

 pollinated flowers have one advantage over wind-pollinated 

 flowers ; they are pollinated by agents which move in definite 

 directions — namely, from flower to flower. Wind-pollinated 

 flowers are pollinated by the wind, which blows the pollen in 

 any direction ; so that for every pollen-grain which reaches the 

 flower of another individual-plant' of the same kind, millions of 

 other pollen-grains fall to the ground and are wasted. The 

 insect-pollinated flower can afford to manufacture less pollen, 

 and is more economical than a flower pollinated by the aid of 

 the wind. The various colours and scents of flowers not only 

 serve to attract insects, but they assist the insect in identifying 

 the flower it wishes to visit. For example, we often see a bee 

 confining its visits to one kind of plant — say a Poppy — during 

 the whole of a morning. The fact that honey is sipped by 

 insects visiting the flowers, together with the fact that wind- 



