358 The Chicago University Text-Book. 
temperament leads him to give full play to it, rather than to state 
the facts of plant-nutrition as an independent series of consecutive 
phenomena and leave the student to try for himself which is the least 
unsatisfactory misfit of the alien word “ food.” 
A little further on the expression “ carbon-assimilation” comes 
in for a not altogether unmerited share of contempt; yet some 
delay in the universal substitution of “photosynthesis ” is justified 
until we know that light really takes part in the synthesis as well 
as in the photolysis. 
There are several careless statements in the sections dealing 
with the intake of carbon-dioxide. On p. 365 it is said that water- 
plants are “ in a very advantageous position as far as a supply of 
C0 3 is concerned because of the great solubility of that gas in 
water,” but the sluggishness of gas-diffusion in water more than 
counterbalances this solubility. 
A little further on it is stated that C0 2 dissolves so readily in 
the wet walls of the mesophyll that the pressure of C0 2 in the 
intercellular passages is usually zero. The evidence is against this, 
and on Horace Brown’s calculation the C0 2 -pressure in the air 
inside the leaf is very little less than that of the air outside. 
The chemical statements about chlorophyll and the accompanying 
plastid-pigments are not at all near to the state of knowledge in 1910, 
and the author has actually introduced a name of his own for pure 
“ chlorophyll,” to wit, chlorophyllin , which is already allotted by 
workers on the subject to a chlorophyll-derivative. 
Chapter IV deals with destructive metabolism. The most 
important of these processes is respiration, to the theory of which, 
Barnes had given special attention. He is strongly of opinion that 
all respiration is primarily protoplasmic breakdown, that food 
material is never oxidised directly in the cell and that the comparison 
of respiration to any sort of combustion is more misleading than 
helpful. He certainly exposes very well our uncertainty as to the 
precise significance of respiration in the cell. 
Fermentation is very briefly dealt with and little sympathy is 
shown with the discovery that alcoholic fermentation can proceed 
apart from protoplasm. 
Chapter V contains the whole of growth and movement, and 
it is in the latter part of this last chapter that one feels that the 
very condensed writing is not quite ideal for treating the more 
subtle difficulties of irritability, though the handling of these is 
otherwise good. 
On the whole this is certainly a well-knit lucid account of the 
