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CHAPTER XV 
THE STORAGE OF RESERVE MATERIALS 
We have seen that the large amount of food which is 
continually being manufactured by a normal green plant is 
very greatly in excess of its immediate requirements, and 
that there is a very extensive system of storage in such an 
organism, by the aid of which it is enabled to survive 
periods, often of some duration, in which the manufacturing 
processes are entirely suspended. We have considered 
further the mechanisms of transport, by which the various 
nutritive substances are transferred from the seats of their 
manufacture to the places in which they are laid up for 
longer or shorter periods. 
The questions of transport and of storage are very inti- 
mately connected. Food once formed is not always moved 
at once to some place where, after a period of storage, it 
will be ultimately consumed. It is often transferred more 
than once, and may occupy several places in succession 
as the demand for it varies. Indeed, we may regard the 
surplus manufactured food, that is the quantity which is 
in excess of the immediate requirements of the constructive 
cells, as a single store, part of which is travelling about the 
plant, and part of which is from time to time withdrawn 
from the travelling stream and laid down in particular 
cells, either to rejoin the travelling current after a longer 
or shorter time, or to be separated from the parent plant, 
and serve as a starting point for the growth and nutrition 
of its offspring. 
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