Chap. II.] 
COURSE OF THE SAP. 
G1 
number of these parts is necessarily attended 
with an increase of nutritive power, and a 
consequent further development of new leaves 
and branches.” 
Again: — 
“ The organs of assimilation, at this period of 
their life, receive more nourishment from the 
atmosphere than they employ in their own sus¬ 
tenance ; and when the formation of the woody 
substance has advanced to a certain extent, the 
expenditure of the nutriment, the supply of 
which still remains the same, takes a new di¬ 
rection, and blossoms are produced. The func¬ 
tions of the leaves of most plants cease upon the 
ripening of their fruit, because the products of 
their action are no longer needed. They now 
yield to the chemical influence of the oxygen 
of the air, generally suffer a change in colour, 
and fall off.” 
The Author of nature, and the author of the 
u Chemistry of Physiology,” form their trees on 
widely different principles. No bud contains 
one leaf only, and perhaps “ a sA^-bud ” would 
be a more proper name than “ a leaf- bud.” But 
whether a bud contains the germs of leaves and 
a shoot, or of a flower and fruit, or of all these, 
these buds are all formed at the same time, and 
