98 PLANT LIFE ON THE FARM. 
struggle is less than that of the grasses and of the legu- 
minous plants. The proportion in which they occur on 
‘the several manured plots is always less than that of the 
grasses, and they never really attain any very great de- 
‘gree of prominence, except in cases where from seasonal 
or manurial causes the grasses are prevented from attain- 
ing their full development. Those species which, like 
Rumex Acetosa, have a powerful underground develop- 
ment, and abundant capacity for collecting and storing 
water, etc., of course have an advantage especially when 
it so happens that they can avail themselves of unoc- 
cupied territory, 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 valua- 
ble possession than is the more robust underground root- 
stock 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 preponderance depends on the 
relative inferiority of the growth of grasses, there are 
also indicationg that some of them are favorably affected 
by certain manures, and others by fertilizing 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 Legu- 
minose. 
Growth of Pasture Plants when unaffected by manure 
of any kind.—The changes from year to year in the vege- 
tation of a plot which has been unmanured for many 
years must obviously be mainly due to seasonal influ- 
ences, and progressive exhaustion of the soil, while those 
