148 
MISCELLANEOUS. 
[Part II. 
There is a con¬ 
stant circulation 
of sap even in 
winter. 
than the other; and when one girths ten feet, 
the other will girth ten feet one inch, which is 
in effect no difference at all. 
Against the theory of the one vernal ascent, 
and the one autumnal descent of the sap, and in 
favour of the constant circulation, or at least 
constant supply of sap, we must consider that 
boughs even of considerable thickness, cut off in 
the autumn, will become dried throughout before 
the spring. But what can account for the mois¬ 
ture of boughs, and even the most, delicate spray, 
exposed at great heights in the air, but the con¬ 
stant supply of sap ? 
Indeed, if the first theory were correct, there 
is no reason why plants should not live through 
the winter out of the ground, and plants taken 
up in the autumn should grow as freely when 
again put in in the spring as if they had just 
been taken up. The contrary of this is the 
case ; the roots of plants taken up in the autumn, 
as well as the plants themselves, unless they are 
“laid by the heel” soon become dry. Why ? 
Because the roots are deprived of the power of 
imbibing moisture. 
I suppose there may be physiologists who 
think the roots of trees useless at all times, 
except to fix the trees ; for if there is no cir- 
