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CHAPTER 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 
constructive 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, 
&e., which it is receiving. Periods of intermission of ir- 
regular duration are caused by differences in these respects, 
. 
