Of Vegetation. 343 
motion of the fap in Evcr-greens, which per- 
fpiring little, their fap moves much more 
flowly than in more perfpiring Trees 5 and 
is therefore much more vifeid, whereby they 
are better enabled to outlive the winters 
cold. It is obferved that the fap of Ever- 
greens in hot Countries is not fo vifeous as 
the fap of more Northern Ever-greens, as 
the fir, for the fap in hotter Countries 
muft have a brisker motion, by means of 
its greater perfpiration. 
Experiment CXXIV. 
In order .to enquire into the manner of 
the expanfion of leaves, I provided a little 
Oaken board or fpatula, a b c d oi this fiiape 
and fize, (Fig. 43.) thro* the broad part at 
a quarter of an inch diftance from each other; 
I run the points of 25 pins x x which flood 
% inch thro*, and divided a fquare inch 
into 16 equal parts. 
With this inftrument in the proper fea- 
fon, when leaves were very young, I pricked 
feveral of them thro* at once, with the points 
of all thefe pins, dipping them firft in the 
red lead, which made lafling marks, 
Z 4 (Fig. 
