The Vegetation Book HI 
which accounts, the Pith doth more eafily tear, and upon tear 
fhrink up, and fo become hollow : as in Cic hory, Lampjana, Sonchus. 
Teafel, Brownwort, and others; wherein the Pores of the Pith are 
Large, and the Sides of the Pores, Thin. Whereas, upon contrary ac- 
counts, the Piths of moft Trees, remain perpetually entire. 
8. 9. THE Reafon why Plants are made thus to become hollow, 
is partly, for the ripening of the Fruit or Seed 3 which is the better ef- 
fected by a more plentiful fupply of Aer continually received into their 
hollow Trunks. 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 Annual Trunks, are hollow: the 
Aer contained in that hollow, drying up the sap, and fhrinking up the 
Sap-Veffels fo far, as to hinder the free motion of the Sap therein 5 from 
whence the P/a»t muft needs perilh. So that as the Content of the 
Aer-Veffils, is a kind of} Vegetable Aer, whofe Office is to Attennate, and 
Ferment the Fujces of Plants : Lo the Content of thele Cavities, cometh 
nearer to a more common 4er, defigned chiefly, fo foon as it is conye- 
nient, to dry them up. 
10. $. AGAIN, astothe Acr-Vefels, divers queftions may be 
asked. As how it comes to, paß, that they are generally lef in the 
Trunk of the fame Plant, than in the Root 2. The Caule whereof is, 
that here in the Trunk they are more under the power of the Aer; 
both that which entreth in at the Truzk , and that which of its own 
Nature afcendeth up into it from the Rost. For the Aer, as we have 
elfewhere faid,is the Mould of the Aer-Veffils 5 to whofe crooked or at 
lcaft, Acid Parts, the saline,and other Principles concurring to their ge 
neration, do conform. To, which they do belt, 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 F; igure of the Particles, not of 
the Aerial, but of the Salime Principle. 
11, $. Wherefore as the Aer-Veffels may be obferved fill tobe dila- 
ted or widened towards the lower parts of the Root; the Aerial Princi- 
ple being there lef predominant, and the Saline more: So towards the 
upper part of the Trak , to be contracted or grow finaller; the Aerial 
Principle being here more predominant, and the Saline leG. 
12. $. FOR the fame caufe it may beobferved, That the Aer-Veffels 
of the Second years Growth, and the feveral years fücceeding, are ufu- 
ally nearer of one Size, than thofe of the Second and Firft; all being 
under a.leß power of the der, than the Firft. For the firlt year the 
Pith being full of Liquor, the Acr-Peffels themfelves, are the only Repo- 
Sitories of the Aer. Whereagafterithe firft year, the Pith becoming dry, 
or another great Repofitory for the Aer 5 the Acr-Veffeles are henceforth 
filled with a moifter or more Vaporous and Saline Aer, and fo made to 
grow wider. 
13. $. Hence the very Size ofthe Pith, hath much influence wpon 
the 4er-Veffels, and the manner of. Nutrition, and the Generation of Li- 
quors in Plants, 
14. $. BUT for the molt part, the Aer-Vefels are fomewhat, 
more or lefs,amplified in every new Annual R ¿orat leaft toa certain 
number of years. Probably, becaufe in the e ler Branches, the Spiral 
Fibres, of which the Vefels confilt, are more bulky; and fo ikon 
Vefe 
