idS The Statural Hiftory 
ficulties^ and no queftion will fatisfie all ufiprejudiced Readers 
how our ^ree comes to flouridi, though difbark'd all round. 
72. But if there fliall be any found fo fro ward, as not to al- 
iow(againft all experience) thofe minute fapveffels in the fubftance 
of the wood^ yet t\\tv\{\\At prick!, d circles between the annual coats 
of the wcod^ obferved alfo by Mr, Willughby^ Mr. Ray^ and Dr. 
Tong % which I fuppofe may be the large air veffeh of Dr. GreWy,, 
may be fufficient for this purpofe ; efpecially in Elm^ where they^ 
are numerous and of two forts, as in Tab. ro. Fig, 2, IK^isrc. 
r s, isrc. It being the office of air vefels^ for about a month in Marck 
and April\ before the new fap veffels of the bark'd.re fit for ufe, to 
convey the fap neceifary for the vegetation of all Plants. And if 
fo, in old trees that have done growing, and have no need of the. 
annual new ])rodu^ion of a bark.-, why may it not continually a- 
fcend by them ftill ? 
73. To which if it be objefted, that a tree lives as well by ve- 
getable air as fap^ and that if the air veffels be continually fiU'd with 
fap^ the tree mufl: dye on the other fide for want of air : It may 
eafily be reply ed, that the ufe of the Infertions or Diametral por- 
tions^ Fig. 2. X Y, interceding the pith at T V W, and the paren- 
chyvia of the bark at GH, all made of fmall kind of bladders. 
clufter'd together, is for conveyance of air^ as well as the airi 
veffels themfelves. But if it be further urged, that, the Diame-. 
tral portions only ferve to convey it by the bredth^ and not the^ 
lengtb of the tree^ which makes them infufficient for this pur-: 
pofe ; we have latitude enough, and can allow the leffer fap vef- 
fels that lye in crofs bars at r 5 to fupply that defed, and ftill re- 
tain all the ranges of the great air veffels -^z IK, LM, NO, PQ , for 
conveyance of the fap^ in fuchlike Trees as our old Elm. 
74. And if it be further enquired, how it comes to pafs that 
fome trees do dye upon the lofs of their bark^ and all are not pre- 
ferved by the help of the fap ^ ox air veffels of the wood: It may 
be anfwer'd, and probably rightly enough, that fuch trees as are 
young, a growing, have a plentiful iffue of thin fap between the 
bark and the vpood^ and that readily bleed when they are wound- 
ed or bored, do moft commonly (if not always) certainly dye: 
whereas fome of the fame trees when older, pad growing, efpe- 
cially if they have a more gummy juice, fuch as Ajh^ Elm^ Lime- 
• Philofoph, Tranfad. iV/<;«i5, 43. d"48. f Dr. Gr^w of the vegetation of Plantsj w/>. i. * 
tree^ 
