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CHAPTEK XIV 



TRANSLOCATION OF NUTRITIVE MATERIALS 



We have so far traced the ways in which plants receive 

 their food, and have examined the processes by which it is 

 appropriated. In some cases, indeed in the vast majority 

 of instances, it is constructed in the interior of the plant 

 by certain of the protoplasts from simple inorganic materials 

 which are absorbed from the environment. In green plants 

 this construction extends to all the substances which can be 

 termed food. In plants without a chlorophyll apparatus 

 the construction is partial only, never going so far as the 

 formation of carbohydrates, though, when these are supplied 

 together with inorganic compounds of nitrogen, proteins 

 and fats can be manufactured. In other cases the con- 

 structive processes are supplemented by the absorption of 

 food in a suitable condition for nutritive purposes, while 

 in others, again, the last method is the only one observable, 

 all constructive power being absent. 



There are other considerations, which must be briefly 

 stated, which have a bearing upon this subject. The con- 

 ditions of life of an ordinary green plant involve a great 

 extension of the original constructive process. It has no 

 definite and regular times at which it can take in a certain 

 quantity of food, which are regulated partly by the needs 

 of the organism and partly by the mysterious factor which 

 we call appetite. Its absorptive processes are much more 

 under the influence of natural phenomena, such as the 

 degree of illumination, the amount of warmth, moisture, 

 &c., which it is receiving. Periods of intermission of 



