THE MOVEMENTS AND HABITS OF PLANTS. 9 



THE STRUGGLE FOE EXISTENCE AMONG SEEDS. 



Pa''e449 Seeds often lie dormant for several years 



in the ground, and germinate when brought 

 near the surface by any means, as by burrowing ani- 

 mals. They would probably be affected by the mere cir- 

 cumstance of haying long lain dormant ; for gardeners 

 believe that the production of double flowers, and of 

 fruit, is thus influenced. Seeds, moreover, which were 

 matured during different seasons will have been subjected 

 during the whole course of their development to differ- 

 ent degrees of heat and moisture. 



It has been shown that pollen is often carried by 

 insects to a considerable distance from plant to plant. 

 Therefore, one of the parents or ancestors of our two 

 plants of Digitalis may have been crossed by a dis- 

 tant plant growing under somewhat different condi- 

 tions. Plants thus crossed often produce an unusually 

 large number of seeds ; a striking instance of this fact 

 is afforded by the Bignonia, which was fertilized by 

 Fritz Miiller with pollen from some adjoining plants 

 and set hardly any seed, but, when fertilized with pollen 

 from a distant plant, was highly fertile. Seedlings from 

 a cross of this kind grow with great vigor, and trans- 

 mit their vigor to their descendants. These, therefore, 

 in the struggle for life, will generally beat and exterminate 

 the seedlings from plants which have long grown near 

 together under the same conditions, and will thus tend 

 to spread. 



PRACTICAL APPLICATION OF THESE VIEWS. 



Under a practical point of view, agricult- 

 ° ' urists and horticulturists may learn something 

 from the conclusions at which we have arrived. Firstly, 

 2 



