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which accounts, the Pith doth more eafilytear, and upon tearing 
fhrink up, and fo become hollow: as in Cichory, Lamplana, Sonchus, 
Leafél, Brownwort, and others; wherein the Pores of the Pith are 
Large, and the Sides of the Pores, Thix. Whereas, upon contrary ac- 
counts, the Piths of moft Trees, remain perpetually entire. 
8. §. THE Reafon why Plants aremade thus to become hollow, 
is partly, for the ripening of the Fruit or Seed which is the better ef- 
fected by a more plentiful fupply of Aer continually-received into their 
hollow Truzks. For by means of that Aer, part of the Sap, isdryed up, 
and the remaining part of it made warmer, and fo fooner matured, 
9. §. Partly, for the better determining the due Age of the Plant. 
Hence it is, that the greater part of Azwual Trunks, are hollow: the 
4er contained in that hollow, drying up the Sap, and fhrinking up the 
Sap-Veffels {o far, as to hinder the free motion of the Sap therein 5 from 
whence the Plant muft needs perifh. So that as the’ Content of the 
Aer-Veffels, is a kind of Vegetable Aer, whofe Office isto Attenuate, and 
. Ferment the Fuyces of Plants: fo the Content of thefe Cavities, cometh 
hearer to amore common Aer, defigned chiefly, fo foon as it is conve- 
nient, to dry them up. 
to. §. AGAIN, asto the Aer-Veffels, divers queftions may be 
asked. As how it comes to pafs, that they are generally lefs in the 
Trunk of the fame Plant, than in the Root 2 The Caufe whereof is, 
that here in the Trw#k they are more under the power of the Aer; 
both that which entreth in at the Tra#k , and that which of its own 
Nature afcendeth up into it’from the Root. For the Aer, as we have 
elfewhere faid,is the Mould of the Aer-Veféls s to whofe crooked or at 
leaft, Acid Parts, the saline,and other Principles concurring to their ge- 
neration, do conform. ‘To which they do beft, the fmaller they are - 
the Fibres of the larger Aer-Veffels making greater Circles, and fo coming 
nearer to a right Line, anfwerable to the Figure of the Particles, not of 
the Aerial, but of the Salve Principle. 
11. §. Wherefore as the Aer-Veffels may be obferved ftill to be dila- 
ted or widened towards the lower parts of the Root; the Aerial Princi- 
ple being there lef§ predominant, and the Szlize more: So towards the 
upper part of the Trwnk , to be contracted or grow finallers the Aerial 
Principle being here more predominant, and the Saline lefs. 
12. §. FOR the fame caufe it may be obferved, That the Aer-Ve/féls 
of the Second years Growth, and the feveral years fucceeding, are ufu- 
ally nearer of one Size, than thofe of the Second and Firfts all being 
under a lefs power of the Aer, than the Firft. For the firft year the 
Pith being full of Liquor, the Aer-Vefféls themfelves, are the only Repo- 
fitories of the Aer. Whereagafterithe firft year, the Pith becoming dry, 
or another great Repofitory for the Aer s the Aer-Veffeles are henceforth 
filled with a moifter or more Vaporows and Saline Aer, and fo made to 
grow Wider. 
13. §. Hence the very Size of the Pith, hath much influence upon 
the Aer-Veffels, and the mannet of Nutrition, and the Generation of Li- 
quors in Plants. 
14. §. BUT for the moft part, the Aer-Vejels are fomewhat, 
more or lefs,amplified in every new. Annual Ring sor at lea{t toa certain 
number of years. Probably, becaufé in the elder Branches, the Spiral 
Fibres, of which the Vefels confift, are more bulky; and fo make a 
Vel 

