278 Of Leaves. 
thorny prickles, upon the edges and tops of divers leaves* 
as barberry, holly, thiftle, furz, &c. 
Cortical thorns are fuch as thofe of the ralberry-bufh, 
being not, unlefs in an invifible proportion, propagated 
from the lignous body. They are of ufe not only for 
the protection of the bud, but alfo for the fupport of 
the plant. 
The ufe of hairs on leaves are to preferve young buds, 
not only from the cold air, but alfo from too much wet, 
which if it were contiguous would often rot and dry 
them. But being made to Hand off in drops, at the ends 
of the hair, does not hurt but refrefh them. Thus we 
fee by the afliftance of the microfcope, that nature often¬ 
times makes the meaneft things fubfervient to the belt 
ends. 
Of the parts and texture of the leaf. 
T H B firft part which here prefents itfelf is the Ikin, 
a fmall bit of which being fcripped off the leaf, 
and laid upon the objeCt carrying glafs R, of fig. 2. or 
held between the nippers, and then placed before the mi¬ 
crofcope, will appear to confifl: of parenchymous and 
lignous fibres, all very curioufly and admirably inter¬ 
woven, as in flag, tulip, &c. 
From hence it is eafy to conceive, that the fkins of all 
plants (as well as thofe of animals) are perfpirable be¬ 
tween the feveral fibres of which they confifl:, formed 
into feveral orifices, either for the better avolation of 
fuperfluous fap, or the admiflion of air ; thefe orifices are 
not in all leaves alike, but varied in bignefs, number, 
fhape, and pofition, and are the caufe of the glofs on the 
upper-fide of the leaves, the backfide having none of them. 
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