324 The Living Plant 



are the Snails, which are said to visit some low-growing flower- 

 spikes of tropical plants for the soft tissue that grows abundantly 

 among the blossoms; and thus they transfer pollen from one 

 plant to another. But the other groups of animals are unavailable, 

 for obvious reasons of habit, size, structure and the like. 



As an earlier chapter (on Protection) has indicated already, 

 plants are obliged not only to develop structures in adaptation to 

 the performance of their functions, but also to protect them when 

 made from hostile external forces which would work their destruc- 

 tion. This is all very true of the highly complicated and greatly 

 exposed flowers. A certain protection against hostile w r eather 

 conditions is attained by a control over the time of blossoming, 

 which occurs in most plants only at times and seasons when the 

 conditions are favorable for cross pollination, the blossoms open- 

 ing in fine weather when insects are about, but not during rain- 

 storms, when they remain under shelter. One of the greatest 

 dangers to which the cross-pollinating mechanisms are liable is 

 the influence of rain on the pollen, for water is absorbed os- 

 motically by many kinds to a degree which causes the bursting and 

 destruction of the grains. Accordingly, in flowers many arrange- 

 ments exist in adaptation to protection of pollen from rain, aside 

 from the great one already mentioned, the failure of blossoms to 

 open in stormy weather. Thus, in a great many blossoms the 

 anthers are safely sheltered under an overhanging upper lip, as in 

 most irregular flowers, like the Mints, Monkshood, and others of 

 horizontal position, while in some kinds they are guarded by 

 bands of unw r ettable hairs. Again, some kinds of flowers close in 

 threatening weather, while others, arranged in flat-topped clusters, 

 turn upside down in a rain-storm, presenting an aspect which 

 leads most people to imagine that they have been beaten over by 

 force of the rainfall. 



But an especial protective need of flowers is against insects that 

 are not adapted to cross pollinate them, and which would remove 

 the nectar without rendering any service in return, against 



