558 BOTANY PART n 



(CHIROPTEROPHILOUS) ; thus the dioecious Pandanaceous plant Freycinetia of 

 the Malayan Archipelago is pollinated by a Flying Fox (Pier opus], which eats the 

 inner bracts. 



Pollination in some cases is effected by means of snails (MALACOPHILOUS 

 PLANTS). To their instrumentality the flowers of Calla palustris, Chryso- 

 splenium, and also the half-buried flowers of the well-known Aspidistra owe their 

 pollination. 



It would seem remarkable that such manifold and various adapta- 

 tions for the conveyance of pollen should exist while the majority of 



FIG. 530. Inflorescence of Marcgravia umbdlata adapted for pollination by Humming-birds. 

 (From SCHIMPER, Plant Geography.) 



angiospermic plants have hermaphrodite flowers ; it is known, however, 

 that the pollination of a flower with its own pollen may result in 

 a poorer yield of seed (Rye) or be without result (self-sterility in 

 Cardamine pratensis. Lobelia fulgens, Corydalis cava, etc.). 



Cross-pollination (allogamy) must take place when the pollen can 

 only germinate if the stigma is rubbed as in the case of Laburnum 

 vulgare. The insect visit, which as a rule will bring foreign pollen, 

 prepares the conditions for germination and excludes the action of the 

 flower's own pollen. In the Orchids the flower's own pollen has a 

 directly injurious influence, and when applied to the stigma causes the 

 flower to wither. 



Even when there is no self-sterility there are many and various 

 conditions which render the self -fertilisation of hermaphrodite flowers 



