42 
POPULAR SCIENCE REVIEW. 
been left unmanured ; others, some twenty in number, have, for 
the last ten or twelve years, been subjected to various manures, 
the constitution and proportions of which are accurately 
determined. The general herbage of the park, like that of the 
unmanured plots, consists of some fifty species of plants, in- 
cluding sundry grasses, clovers, docks, umbellifers and other 
plants commonly found in such situations. In the several 
manured plots a change is observable, sometimes slight, at 
other times vast, and the change does not show itself so much 
in the superior luxuriance of any one plant, or in the starved 
condition of another, as it does in the more or less complete 
exclusion of certain plants, and in their replacement by others. 
Thus, while the unmanured plots contain, say, fifty species of 
plants, others comprise less than half that number ; from some 
plots the clovers and umbellifers are banished altogether, while 
in other cases they may be proportionately increased. Even 
among the grasses the competition is very severe, and the 
result in some cases is that all or nearly all have to give way 
to the cock’s-foot grass {Dactylis ccespitosa), the growth of 
which is so fostered by certain manures as to cause it to over- 
come its fellows and remain master of the situation. To the 
plots to which a mixed mineral manure, consisting of salts of 
potash, soda, magnesia, and lime is applied, but little difference 
in the number of species is observable. On the other hand, 
manures containing ammonia salts, or nitrates, cause a great 
diminution in the number of species living in the plot to 
which they are applied. While the unmanured plots furnish 
by weight about 60 per cent, of grasses, the remainder, con- 
sisting of plants of other families, the plots to which admix- 
ture of mineral and nitrogenous manures is added contain as 
much as 95 per cent, of grasses, and these belonging to a com- 
paratively very few species. Salts of potash and lime, which 
are comparatively inert as regards grasses, manifest their infiu- 
ence in increasing the vigour and the absolute numerical pro- 
portion of the leguminous plants. 
The manner in which these results have been arrived at is 
worthy of a short description in this place. 
Notes are taken at frequent intervals during the season of 
growth, the appearance of the plants noted, their relative 
luxuriance observed, and their comparative tendency to produce 
flower or stem and leaf, the abundance of flowers, &c., &c. 
Eoot-growth is studied, and also the character of the soil in the 
various plots, and the way in which its texture and its capacity 
for holding or transmitting water are modified according to the 
manure applied. When the crop is cut from each plot, its 
weight is estimated, and also the amount of dry produce. In 
some cases chemical analysis is pushed further, and the ashes 
