ON THE SEASONAL GROWTH OF PLANTS. 451 
will subsequently come forth to make up the loss, and the seasonal 
growth he greatly prolonged. 
From all these observations, and from the instances adduced, we are 
led to infer that the great majority of plants are more or less seasonal, 
that they have periodical states of action and repose, and in many cases 
we have reason to suppose that the completion of the first depends on 
the perfection of the second. 
Whether plants, like animals, require rest, is a question which can be 
answered only by the facts observable as relative to them. That they 
have rest from this change of seasons is manifest; and that they take 
rest when their paroxysm of growth is over, is equally obvious. Many 
of them even appear to sleep; for as soon as the light of the sun is 
withdrawn, their winged leaves drop from their erect or horizontal 
position, and hang listlessly till the next dawn of day. Thus it would 
seem that plants require to be restored after the excitement of the 
summer. But we have further to inquire whether this rest be neces¬ 
sary, and whether plants be invigorated thereby ? That it is necessary 
is obvious, because it is an incident in the course of nature; and that 
they are recruited in their vegetative powers, may be believed, by com¬ 
paring the vernal with the autumn growth ; their winter rest is only a 
kind of torpidity, in which their vital action is not wholly repressed. 
There is always some visible motion, however slow, particularly in the 
swelling of the buds, the emission of root fibres, and the occasional 
oozing of sap from a wound made on the south side of a tree, even in 
the depth of winter. And as the interior of a stem is always warmer 
than the surrounding air, there may be some kind of elaborating or 
assimilating process going on, which may have a chemical effect in 
changing the crude sap imbibed in the summer into a richer and more 
excitable fluid better fitted for expansive action in the spring. 
Practical experience has assured us that a tree which has been de¬ 
bilitated by removal, drought, or from other casualty, and consequently 
destitute of the necessary share of this matured sap, shoots feebly, and 
produces few or no perfect fruit ; and in the business of forcing fruit 
trees, we can very frequently see that if one has been exhausted either 
by very early or repeated forcing, or from bearing a great crop of fruit, 
it is less able to be forced early, or to bear a heavy crop in the following 
year. This consequence is often visible in the open air, where we 
rarely see two heavy crops following each other. 
It is of the utmost importance to the fruit grower to keep his trees in 
that thrifty condition, that they shall never become debilitated by over¬ 
bearing, or for want of due nourishment, and particularly that they be 
always charged with a full supply of elaborated sap, and which is 
