280 
PHYSIOLOGY. 
BOOK II. 
bark ; and of a more or less conical figure. At the axil of 
every leaf a new growing point had been generated during the 
growth of the axis ; so that the shoot, when deprived of its 
leaves, is covered from end to end with little, symmetrically 
arranged, projecting bodies, which are the buds. 
The cause of the figure of the perfect shoot being conical 
is, that, as the wood originates in the base of the leaves, 
the lower end of the shoot, which has the greatest number of 
strata, because it has the greatest number of leaves above it, 
will be the thickest ; and the upper end, which has had the 
fewest leaves to distend it by their deposit, will have. the least 
diameter. Thus that part of the stem which has two leaves 
above it will have wood formed by two successive deposits ; 
that which has nine leaves above it will have wood formed by 
nine successive deposits ; and so on : while the growing point, 
as it can have no deposit of matter from above, will have no 
wood, the extremity being merely covered by the rudiments 
of leaves hereafter to be developed. 
If at this time a cross section be examined, it will be found 
that the interior is no longer imperfectly divided into two 
portions, namely, pith and skin, as it was when first examined 
in the same way, but that it has distinctly two internal, per- 
fect, concentric lines, the outer indicating a separation of the 
bark from the wood ; and the inner, a separation of the wood 
from the pith : the latter, too, which in the first observation 
was fleshy, and saturated with humidity, is become distinctly 
cellular, and altogether or nearly dry. 
III. With the spring of the second year, and the return of 
warm weather, vegetation recommences. 
The uppermost, and perhaps some other, buds, which were 
formed the previous year, gradually unfold, and pump up sap 
from the stock remaining in store about them ; the place of 
the sap so removed is instantly supplied by that which is next 
it; an impulse is thus given to the fluids from the summit to 
the roots; fresh extension and fresh fibrils are given to the 
roots ; new sap is absorbed from the earth, and sent upwards 
through the wood of last year ; and the phenomenon called 
the flow of the sap is fully completed, to continue with greater 
or less velocity till the return of winter. The growing point 
