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CHAPTER XIII 
OTHER METHODS OF OBTAINING FOOD 
In our introductory considerations of the true nature of 
the food of plants, and of the manner in which they obtain 
it, it was pointed out that there are stages in the life- 
history of all plants during which it is imperative that they 
shall be supplied with food in a form in which they can 
assimilate it at once, constructive mechanisms either being 
altogether absent from them or not having been developed 
at the particular time under consideration. There is thus 
in every plant a power of assimilating organic food so 
supplied, a power which in some cases is permanently 
relied upon, sometimes completely, sometimes only partially, 
and which in other cases is laid aside as soon as the 
chlorophyll apparatus becomes developed. The need for 
the supply of the organic food is always felt by every 
protoplast, and the latter cannot be nourished except by it. 
We may contrast in this respect the individual proto- 
plast and the colony of which it is a member, the latter 
being able through the co-operation of its mdividuals to 
construct the organic food which must be provided for 
the use of every member, even of those to which the work 
of construction is allotted. 
The constructive power may be partially or wholly lost 
or undeveloped ; in such cases the loss must be compensated 
for by the supply from outside of the material the plant is 
not able to synthesise for itself. 
Examples of plants possessing different powers of such 
