TRANSLOCATION OF NUTRITIVE MATERIALS 215 
These considerations lead us to the conclusion that when 
the absorption of food or food materials by a plant is pro- 
ceeding, the probabilities are decidedly in favour of such 
an absorption bemg much greater than the immediate 
need for direct consumption. The constructive process, 
followed by the accumulation of its products, is certainly 
the leading one in the history of the different members 
of the vegetable kingdom. Most of it is ultimately devoted 
to the increase of the framework which attends upon the 
multiplication of the protoplasts, which we commonly speak 
of as growth, and proceeds for such long periods that there 
is accumulated in such a structure as a forest tree an enormous 
amount of material and of potential energy. 
But this latter form of accumulation, devoted especially 
to the production and maintenance of a very large plant- 
body, differs materially from the storage of a quantity of 
food which is temporarily a surplus, but which is destined 
for subsequent consumption by the protoplasts. This is 
a feature of the life of all plants in varying degrees, whether 
they form a large plant-body or not. We must turn to 
examine this surplus production in more detail. 
In an earlier chapter we alluded to the very marked 
division of labour which we can observe in such a com- 
munity of protoplasts as form a large plant. We have 
since studied certain of the different processes which are 
carried on by particular tissues or collections of protoplasts, 
rendering them unable to perform other necessary duties. 
It is evident that to enable them to discharge their special 
functions they must be fed and nourished. It is equally 
clear that they are not living under conditions which enable 
them to construct food for themselves. We see that it is 
consequently necessary for food to be transported to them 
from the seat of its construction. 
There is in every green plant a localised, though fairly 
widespread, region in which construction is taking place, 
and there are other equally well-defined regions which 
must be supplied with food transported from the seats of 
