344 Of Vegetation. 



hairy fibres are inferted into the angles of the 

 furrows in the Walnut-fhell : Their ufe is 

 therefore doubtlefs to carry in thofe long di- 

 flin<ft veffels the very vifcous matter, which 

 turns, when dry, to a hard (hell ; whereas, 

 were the fhell immediately nourifhed from 

 the foft pulpous hull that furrounds it, it 

 would certainly be of the fame foft conftitu- 

 tion, the ufe of the hull being only to keep 

 the fhell in a foft ductile ftate, till the Nut has 

 done growing. 



We may obferve the like effect of a flower 

 motion of the fap in Ever-greens, which per- 

 fpiring little, their fap moves much more 

 flowly than in more perfpiring trees, and is 

 therefore much more vifcid, whereby they 

 are better enabled to out-live 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 Ever-greens, as the Fir, 

 &c. for the fap in hotter countries muft have 

 a brisker motion, by means of its greater per- 

 fpiration. 



Experiment CXXIV. 



In order to inquire into the manner of the 

 expanfion of leaves, I provided a little oaken 

 board or fpatula, a b c d y of this fhape and 



fize 



