344 VEGETABLE PHYSIOLOGY 
CHAPTER XXII 
THE PROPERTIES OF VEGETABLE PROTOPLASM 
Tue influence of the environment upon the structure of 
plants we have seen to be far-reaching. Different con- 
ditions of the surroundings are followed by differences of 
structure, which are greater in proportion as the time 
during which those conditions act is more and more pro- 
longed. The living substance of the plant is clearly the part 
influenced by the environment, for we have seen that the 
skeleton and other non-living parts of the plant owe their 
construction to its activity. We may therefore with advan- 
tage pause at this point to examine a little more closely 
the properties which are exhibited by vegetable proto- 
plasm. 
We have seen throughout all the foregoing chapters 
that all the processes which conduce to the well-being of 
the plant are, to a large extent, if not entirely, under the 
control of the living substance. Though the absorption 
of its food materials from the air and the soil is due to 
physical processes, these are nevertheless largely regulated 
by the behaviour of the protoplasm under all sorts of vary- 
ing conditions, The manufacture of food from these crude 
materials, and its subsequent distribution, the accumu- 
lation and dissipation of energy, the processes of nutrition 
and growth, are all subject to the same regulation. 
But there are also other properties of protoplasm which 
have not so far been more than incidentally referred 
to. The plant exhibits particularly the power of appre- 
ciating changes in its surroundings, and is capable of 
adapting itself in various ways to such changed conditions. 
