250 Of the pith of Roots'. 
fee. many roots that have no pith at their lower part, 
have one at the top, as columbine, lovage, &c. Their 
contexture by the microfcope, appears to be of the fame 
general kind in all plants, both in the parenchyma of the 
bark, in the infertment or diametrical portions, and in the 
pith, all being compofed of bladders, which are of very 
different fizes, feldom lefs than thofe of the bark, as in 
afparagus, fig. 467. but generally much bigger, as in 
horfe-raddifh, fig. 473. their pofition feldom varies, but is 
uniform in a tranfverfe fedlion of all parts of the root 
piled up evenly one over another. In an upright fection 
they feem to run in diredf trains, length-ways 5 they are 
for the mod; part orbicular, though in the larger roots 
fiomewhat angular* On obferving thefe bladders with 
the microfcope, their fides will be found to confift of fe- 
veral ranks of exceeding fmall fibres, lying for the mod: 
part evenly one over another, from the bottom to the top 
of every bladder, and running a-crofs alfo from one bladder 
to another. If the pith be cut with a fharp razor, or 
penknife, and fo applied to the microfcope;, they will be 
feen diftmdlly. 
All plants exhibit this fpedlacle, hut thofe bed with: 
the larged bladders ; nor the fame pith fo well in any 
other condition, as when dry; becauie then the fap being 
voided, the fpaces between the fibres, and the fibres them- 
felves are more didinctly feen. Yet it mud not be dried 
after cutting, becaufe its feveral parts will thereupon 
coincide and become deformed, but to be chofen while 
the, plant is growing, at which time it may be often found 
dry and not deformed ; as in the trunks of common thidle, 
Jerufinem artichoke, &c. cut off the white bottoms of the 
bladders of a bullruih tranfverfly, and they will appear 
like a curious piece of needle-work. The whole body 
of 
