189 



CHAPTEK 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 individuals 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 



