336 PLANT-LIFE 



is liable to the attacks of many predatory foes, as well 

 as climatic exigencies. Without doubt it is during the 

 seedling period that the plant is most vulnerable, and 

 that the issues of its existence are most problematical. 

 The mortality among seedlings must be exceedingly 

 high. Herein we see the necessity for the production 

 of abundance of seeds; they must not only be pro- 

 duced in sufficient numbers to provide against wastage 

 in dispersal, but also against high infantile mortality. 

 The species survives by force of numbers. Nature 

 is careless about individuals. It is the race that counts, 

 and it usually happens that the individuals which sur- 

 vive in the struggle for existence are the best fitted 

 to exist, and thus be the means of perpetuation of a 

 vigorous race. 



We have already discussed (p. 264) means of assuring 

 a satisfactory transpiration current and devices which 

 prevent it being unduly checked. We have in the 

 same place indicated some methods of avoiding ex- 

 cessive transpiration. The all-important stomata are 

 usually most numerous on the undersides of leaves, 

 where they are variously protected lest they should 

 suffer interference in the exercise of their duty. The 

 tender protoplasts of leaves and other green parts are 

 screened from excessive heat and light and fortified 

 against rain and hail in various ways. 



All parts of plants are subject to the attacks of 

 fungal and bacterial fiends. Spores and germs are 

 almost omnipresent, floating about in the air, and 

 seeking some weak point in a plant's defences where 

 they may find lodgment and flourish. They induce 

 some of the most devastating diseases. It so happens 



