THE BATTLE OF LIFE. 99 



in different species, this root- growth is hoth superficial as 

 well as deep. In addition to this generally ample root 

 development many of the species are aided in the struggle 

 by their stout tufted habit and specially by their power of 

 producing creeping offshoots above or below ground which 

 insinuate themselves in between other plants and occupy 

 any vacant territory. No doubt internal anatomical differ- 

 ences are even of greater moment than these external 

 characteristics, but these demand minute comparative 

 study by means of the microscope, under various con- 

 ditions, and at different seasons, and constitute a branch 

 of inquiry at present hardly even entered upon. 



Although grasses as a whole comport themselves in a 

 particular manner distinct from that of the other tenants 

 of the plot, yet it is found that individual grasses, and even 

 members of the same genus, vary very much among one 

 another. 



It is instructive to compare the different tendencies of 

 the two most generally prevalent grasses, Festuca ovina 

 and Agrostis vulgaris. As to structural endowments they 

 would seem to be not unfairly matched, but the Festuca is 

 conspicuously worsted on the plots highly dressed with 

 nitrogenous manures, while the Agrostis is befriended by 

 them, and its vigour and tufted habit are increased. Poa 

 trivialis and Holcus lanatus afford contrasts of a similar 

 character, the Poa being largely increased by nitrate of 

 soda, while the Holcus is similarly acted on by ammonia 

 salts. Of the same character are the differences observable 

 between Agrostis vulgaris, which is influenced by ammonia 

 salts, and Holcus lanatus, Avena pubescens, and Avena 

 flavescens, which are especially acted upon by nitrate of 

 soda. Very marked contrasts between species of the same 



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