vn] PLANT POPULATION 115 



examples illustrate the magnitude, and the far reach- 

 ing character of the results which may follow, in 

 cases where the immense potentialities conferred upon 

 organisms by the geometrical ratio of increase are 

 combined with effective means of dispersal. Most 

 plants possess some such potentialities, but few find 

 the opportunity of realising them. 



The failure in so many cases leads us to enquire 

 what becomes of the enormous surplus of potential 

 lives which never get beyond the initial stage of the 

 germ ? The fact is that the risks of youth are very 

 great indeed. Many germs are killed off almost at 

 once by unfavourable conditions, such as undue 

 temperature, or drought. Light affects some injuri- 

 ously, and happily this is the case with many Bacteria. 

 Many fail to find a suitable nidus for germination ; 

 others succumb to unsuitable seasonal changes in the 

 defenceless condition of the seedling. Competition 

 crowds out others. Many fall victims to the predatory 

 attacks of animals, which naturally divert to their 

 own uses any food-stores designed for the germ. 

 Fungal attack accounts for the failure of others, and 

 especially in the seedling state. When we contem- 

 plate the multiplicity and the insistence of these risks, 

 the cause for astonishment is rather that any come 

 through the ordeal than that so many fail. There is, 

 however, a more occult series of obstacles to success 

 than those which have been mentioned, and though 



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