J 



Of Vegetation. 343 



motion of the fap in Evcr-grccns, which per- 

 fpiring little, their fap moves much more 

 flovvly than in more pcrfpiring Trees > and 

 is therefore much more vifcid, whereby they 

 are better enabled to outlive the winter's 

 cold. It is obferved that the fap of Ever- 

 greens in hot Countries is not fo vifcous as 

 the fap of more Northern Evcr-greens, as 

 the fir, &c. for the fap in hotter Countries 

 rauft 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 of this fhape 

 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 

 i 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 

 feveralof them thro' at once, with the points 

 of all thefe pins, dipping them firft in the 

 red lead, which made lading marks. 



Z 4 ( Fi S- 





,:*' 





-f 



