REPORT OK VARIOTJS MANURES AT CHTSWrCK. 
75 
of different plants on soil and atmospheric conditions respectively, 
the effects of varying conditions as to soil- supply, the tendency to 
luxuriance on the one hand or to maturation on the other, or the 
widely varying special characters of development, according to the 
external conditions provided, are points which, when thoroughly 
investigated and generally understood, must serve to place the cul- 
tivation of plants for various purposes — whether for the supply of 
wood, of fibre, of food, of drug or colour in some special organ,, 
of fruits, or of flowers — on the sure basis of scientific principle, 
rather than leave it dependent on the still uncertain, though often 
wonderfully successful, guidance of empiricism. May not such 
knowledge too, give much insight into the varying functions of 
plants which have been held to be allied to, or separated from, 
each other, as the case may be, for reasons quite independent of 
the sources of their accumulation, or the special tendency of 
their assimilative actions ? 
