14 H. G. SMITH. 
The demonstrated results of life effort are now recognised 
as being largely due to chemical action, and extended 
investigations of the chemical and physical causes which 
are responsible for these changes would throw considerable 
light on the metabolic processes of the plant, the value of 
the results being, of course, governed largely by the extent 
of the observations, and on the completeness with which 
they have been undertaken. 
Professor Vines has admitted that in studying the differ- 
entiation of the cell wall the botanist received valuable aid 
from the chemist, and research in this direction probably 
began with Payen’s discovery that the characteristic and 
primary chemical constituent of the cell wall is a carbo- 
hydrate which he termed cellulose. This is only one of 
numerous instances of appreciation; but it is to the slow 
accumulation of isolated chemical facts such as this, that 
we may hope to arrive at more definite conclusions as to 
the chemical reactions by which pronounced anabolic 
changes are brought about, and the directions in which the 
substances thus formed are utilised. 
Darwin was evidently convinced that chemical conditions 
influence greatly the growth and characterisation of plants, 
because in the first chapter of the Origin of Species he 
writes :—“‘such facts as the complex and extraordinary 
out-growths which variably follow from the insertion of a 
minute drop of poison by a gall producing insect, show us 
what singular modifications might result in the case of 
plants from a chemical change in the nature of the sap.” 
It would be possible, of course, to multiply references of 
a Similar nature, but these are sufficient to indicate the 
opinions of workers generally on the effect of chemical 
influences in the establishment of natural floras. 
In dealing with genera of economic importance it is, of 
course, the utilitarian side of the question which dominates, 
