TRANSLOCATION OF NUTRITIVE MATERIALS 209 
the absorption of food or food materials by a plant is 
proceeding, the probabilities are decidedly in favour of 
such an absorption being 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. The increase of the framework 
which attends upon the multiplication of the protoplasts, 
which we commonly speak of as growth, proceeds for such 
long periods, moreover, that there is stored up in such a 
structure as a forest tree an enormous amount of material 
and of potential energy. 
But this latter form of storage, devoted especially to 
the production and maintenance of a very large plant-body, 
differs materially from the accumulation 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 trans- 
ported 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 
its manufacture. The cell or protoplast, which contains a 
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