310 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 dis- 
appearance 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 construction 
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 
