270 Of the Pith of Trees. 
The parenchyma of the pith is compofed of bladders 
the very fame with thofe in the bark, and oftentimes in 
the infertions within the wood 3 only thefe of the pith are 
largeft, thofe in the bark lefs, and thefe in the infertions 
Ieaft of all. 
The bladders of the pith, though always comparatively 
great, are of very different fizes. Thofe of thiflle, borage, 
&c. appear in the microfcope like the cells of an honey¬ 
comb 3 the bladders in common thiflle and borage, are 
fo large as to contain within their horizontal area, about 
twenty bladders of the pith of oak. Wherefore one blad¬ 
der in thiflle is at leafl an hundred times bigger than an¬ 
other in oak. 
The fhape of the pith bladders admit of feme variety ; 
they are for the moft part round, yet oftentimes angular, 
as in reed grafs, a water plant 3 where they are alfo cu¬ 
bical 5 in borage, thiflle, and many others they are pent¬ 
angular, fexangular, and feptangular. \ 
As to the texture of thefe pithy bladders, they are 
oftentimes compofed of fmaller ones, as in borage, bulrufh, 
and many other plants. 
Whence it appears, that as the veffels of plants, viz. 
the air veffels and lymphsedudts, are made up of fibres, 
fb the pith, or the bladders of which the pith confifls, 
are likewife compofed of fibres, which is alfo true of the 
parenchyma of the bark, and of the infertions in the 
wood, and even of the fruit, and all other parenchymous 
parts of a plant, and that the very pulp of an apple, pear, 
cucumber, plumb, or any other fruit, is nothing elfe but 
a ball, of moft extreamly fmall tranfparent threads or 
fibres, joined together in a different, but curious manner, 
even all thofe parts of a plant, which are neither formed 
into vifible tubes, nor bladders, are made up of fibres 3 
and though It be difficult to difeover them in thofe parts 
' a. which 
