224 The Eothamsted Grass Experiments. 



growing in the meadow is dependent much less on the 

 chemical composition of the soil than on its physical character, 

 its capacity for holding water, and its permeability to roots. 

 The immediate source of victory lies very generally in the 

 powerful root-growth of the survivors, the term " root " here 

 covering all kinds of underground stem. The various 

 influences affecting the struggle for existence amongst 

 meadow plants are discussed by the authors in a fascinating 

 manner, and this part of the memoir is of special value to the 

 botanical student. 



Every plant occurring on the plots is dealt with individu- 

 ally, and in the case of each grass and leguminous plant and 

 of the more commonly occurring weeds, a table showing the 

 relative predominance is given. The fact that plants closely 

 allied morphologically may yet differ widely in their physio- 

 logical endowments is strikingly illustrated by the two species 

 Poa trivialis and Poa pratensis. These two plants, sprung at 

 some former period from a common ancestor for this, we 

 presume, is the morphological significance of their being 

 placed in the same genus differ only in the most trivial 

 points : Poa pratensis (smooth-stalked meadow grass) is 

 smooth, stoloniferous, and has a blunt ligule ; Poa trivialis 

 (rough- stalked meadow grass) is rough, has no stolons, and 

 possesses a long pointed ligule. We read that " the stolon- 

 bearing Poa pratensis is especially benefited by nitrogenous 

 manure in the form of ammonia-salts (in combination with 

 mineral manure), but not at all by nitrate of soda, whereas 

 the more finely-rooted and non- stoloniferous Poa trivialis has 

 declined markedly on the ammonia plots, but has remained 

 very prominent on the nitrate plots, especially where the 

 larger amount of nitrate was used with the mixed mineral 

 manure." Thus in 1872, on plot 9 (mineral manure and 

 ammonia- salts), Poa pratensis gave 22'67 per cent of the total 

 produce, and Poa trivialis only 0'64 ; on plot 14 (mineral 

 manure and nitrate of soda) Poa trivialis gave 2476, and 

 Poa pratensis only 2'57 per cent. It is suggested that the 



