ADVANTAGES OF KNOWLEDGE OF VEGETABLE PHYSIOLOGY. 187 
imitate them, it is obvious, as a general rule, the more healthily 
will they grow. Thanks, however, to this very power of self, 
adaptation, they can accommodate themselves within limits to 
their new environments in a hothouse, greenhouse, or open 
border in England. Still, the more that is known about their 
habits in nature, so much the better for the cultivator. Thus, 
it is said that when Aucuba japonica was first introduced from 
Japan, it was grown under glass; but a stray plant having been 
thrown away was discovered to have lived through a severe 
winter, so that it has ever since been grown in the open. A 
gardener thus finds by experience, often after many mistakes— 
which cost money — how to grow foreign plants; but his 
knowledge may have been acquired laboriously ; and he may 
even then not know why it is best to do this or that for his 
plants. It is here that a knowledge of physiology can some¬ 
times step in and tell him ; for it is the province of science to 
investigate into causes. Nature, however, and especially the 
department of “ life,” is so obscure that no scientist has ever 
probed all her secrets to the bottom, and probably never will be 
able to do so; until she tells us how it is that life-forces can issue 
out of food. However, no one can cultivate a plant at all without 
knowing something of its physiological requirements to enable 
it to live and thrive ; and just so far as the practical man 
succeeds, so far is he acquainted with the main facts of physiology. 
The question is, therefore, Does he know enough ? 
Illusteations.— It will not be amiss to review the organs of 
a plant in order to consider briefly their functions in a general sort 
of way. It will then be seen that there is really no great mystery 
in physiology after all. In order to illustrate the preceding 
remarks let us commence with a few physiological observations 
on germination. 
Germination .—Seeds must be moist throughout. There must 
be a proper temperature ; and a free circulation of air. The first 
and second are necessary in order that the various chemical 
changes may take place within the seed; the third is required 
for respiration. This shows the importance of avoiding too great 
a depth or too wet a soil. The radicle, on protruding, points 
earthwards. This is due to gravity. If the radicle be placed 
in a horizontal position, gravity acts on the tip ; but the 
influence is conducted to a certain distance behind it, where the 
