304 VEGETABLE PHYSIOLOGY 
CHAPTER XIX 
GROWTH 
In studying the growth of plants we must bear in mind 
the relation which it bears to the processes of metabolism 
which we have already discussed. We have seen that the 
constructive processes, partly anabolic and partly kata- 
bolic, are much greater than those which lead to the 
disappearance of material from the plant-body. The result 
of this is that there is a conspicuous increase in the 
substance of the plant, as well as an accumulation of 
potential energy which can be made use of by the plant 
through various decompositions which its protoplasm can 
set up. The great permanent accumulation of material is 
what we associate with the processes of growth. Here, 
however, we must distinguish between the increase of the 
living substance, which is essentially an anabolic process, 
and that of the manufacture of the framework, the con- 
struction of cellulose, wood, cork, and other products, which 
is the result of katabolism. 
The growth of the living substance is always the result 
of constructive metabolism, and is attended by an increase 
of bulk and weight. The growth of an organ sometimes 
appears to be independent of such increase of weight: 
indeed, a diminution of the weight of the whole structure is 
sometimes noticeable. For instance, in the case of a potato 
tuber allowed to germinate under such conditions as 
prevent the absorption of food materials from without, we 
meet with a marked change of form, but, owing to. the loss 
of moisture by transpiration, and of carbon dioxide as a 
consequence of its respiration or the katabolic processes 
