THE BATTLE OF LIFE. 103 



which they seize and hold with great success against all 

 comers, and also in cases where the density of the soil is 

 such as to offer" an obstacle to the penetration of fibrous 

 roots. But, on the whole, the dense fibrous net-work of 

 roots made by the grasses, which enables them to avail 

 themselves of well nigh every particle of soil within their 

 reach, is a more valuable possession than is the more 

 robust underground rootstock possessed by several of the 

 miscellaneous plants. Most of the species occur in too 

 insignificant amounts to be considered as anything more 

 than accidental tenants, and while in others their prepon- 

 derance depends on the relative inferiority of the growth of 

 grasses, there are also indications that some of them are 

 favourably affected by certain manures, and others by fertilis- 

 ing agents of different character. But on the whole, these 

 indications observed on plants growing in association are 

 by no means so marked as in the cases of the grasses and 

 the Leguminosae. 



Growth, of pasture plants when unaffected by manure 

 of any kind The changes from year to year in the 

 vegetation of a plot which has been umnanured for many 

 years must obviously be mainly due to seasonal influences, 

 and progressive exhaustion of the soil, while those which 

 are observed in the manured plots are as obviously brought 

 about, partly by the manures and partly by climatal changes. 

 The produce of hay at Rothamsted, without manure, has 

 varied from 8 to 39 cwts., the average for twenty-five years 

 having been, as before stated, 23 cwts. per acre. This hay 

 is made up on the average of forty-nine different species 

 in different proportions, as determined by rigid comparative 

 scrutiny. Of the forty-nine plants, seventeen are grasses, 



