xxxiv MORPHOLOGY OF FLOWER 469 



By the time this takes place the stamens have dehisced, 

 i.e., split down each side, so that the two pollen-sacs of each 

 half-anther discharge their pollen by a common slit (Fig. 125, 

 B 2 ). The pollen is usually not dry like that of Gymnosperms 

 but sticky, so that the grains are not readily blown away but 

 tend to adhere to one another and to the ruptured anther. 

 Thus, when the insect inserts its head into the flower a 

 greater or less quantity of pollen is certain to stick to 

 it, and to be carried off as the insect flies to another 

 flower. 



It will be remembered that the stigma is covered with 

 sticky hairs, the consequence of which is that as the insect 

 flies from flower to flower, the pollen it has collected from 

 the stamens of one is transferred to the stigmas of another, 

 and thus, in all the higher Angiosperms, pollination is effected 

 by the agency of insects and not, as in Gymnosperms, by the 

 chance action of the wind. 



Thus the corolla serves an attractive purpose : by its 

 colour and scent insects are informed of the store of nectar 

 it contains, and in the search for that food they uncon- 

 sciously benefit the plant by performing the work of pollina- 

 tion. In this way pollination is made more certain than 

 when left to the wind, and the plant is saved the production 

 of the immense quantity of pollen essential to a wind- 

 fertilised plant, in which a very small fraction of the grains 

 produced can possibly find their way to a female cone. 



Still another striking feature of the angiospermous as 

 compared with the gymnospermous flower is the shortening 

 of its axis. A comparison of Fig. 126, A, with Fig. 119, 

 A and c, shows that the floral receptacle (fl. r) of the Angio- 

 sperm is nothing but the axis of the gymnospermous cone 

 shortened and broadened. The natural result is the suppres- 

 sion of the mternodes and the consequent approximation 



