MANURING 55 



to say from analysis of the ash of a plant what proper 

 manuring should be. This is, as I have pointed out, a 

 question not to be answered from an examination of 

 the ash alone, but has to be taken in conjunction 

 with the soil on which a plant is grown and the power 

 which that plant has of attracting various soil ingre- 

 dients, in short, it has to be the work of experimental 

 inquiry." 



Dr. Voelcker sums up his lecture with further pointed 

 remarks of the highest importance to the cultivator, in the 

 presence of the fact that it is popularly supposed that the 

 chemist is able to decide by analysis alone many points 

 which it is absolutely necessary should be decided, which 

 can only be decided by cultivation experiments ; and 

 it is only when theories are proved by actual experiment 

 in the field that the doctrines of the laboratory should be 

 adopted for general use. He says : " While I have in the 

 foregoing put out some points in which a knowledge of 

 chemistry may be useful for the better understanding of 

 the processes which go on in plant life and growth, and for 

 the application or practice of the principles which have 

 been laid down, it is only right that I should indicate some 

 of the limitations which have to be put, in short, to name 

 some of the things which chemistry cannot do. First 

 among these I would admit that chemistry has yet failed 

 to give any explanation as to why one plant likes this or 

 that particular ingredient, or rejects one or the other. 

 What the particular ingredients do in plant structure, or 

 how their absence would be felt, remains a matter of 

 further inquiry. So that there has not yet been given 

 any adequate explanation as to why one plant will grow 

 on a particular soil and not on a different one, why potatoes, 

 for example, will grow well in a sandy loam, and not in a 

 heavy clay, while fruit-trees and hops need a fairly heavy 

 soil. Again, chemistry has not solved the question of how 

 to produce quality and flavour without sacrifice of quantity. 

 In what, indeed, quality and flavour consist is itself a 

 mystery." 



