THE BATTLE OF LIFE. Ill 



growth of Poa prate?isis, Agrostis vulgaris, Festuca ovina 

 &c., more than does the admixture of mineral and 

 nitrate. On the. other hand, the following species, among 

 others, are more benefited by mineral and nitrate than by 

 mineral and ammonia : Poa trivialis, Dactylis glamerata, 

 Bromus mollis, and Lolium perenne, &c. 



In some seasons, especially in years of drought, (1870), 

 Bromus mollis was extremely prevalent, its deep roots 

 giving it an advantage over others. 



Effects of change of manure. The object sought at 

 Rothamsted in changing the conditions of manuring 

 has been to ascertain definitely to what particular ingre- 

 dient in a mixed manure a particular effect is due, and to 

 obtain confirmation of the results obtained by other 

 methods. By adding or by withholding a particular salt, 

 as the case may be, an answer to the question proposed 

 may be obtained. In the following paragraphs the effects 

 of the disuse of certain manures, and then of the substi- 

 tution of one kind for another, will be very briefly 

 alluded to. 



Disuse of manure of any kind. On a plot to which 

 farm-yard manure was applied it was observed that while 

 the produce was largely increased, more so indeed than 

 under almost any other circumstances, the per-centage of 

 grasses and of some of the miscellaneous weeds was 

 increased, while the leguminous herbage was diminished. 

 On discontinuing the dung the vegetation of the plot was 

 observed gradually but uniformly to approximate to that 

 of the unmanured plot, the number of species increasing 

 without any marked preponderance of any, and good grasses 



