For in al 
Der margin 
that ftand 
cir Situs 
jin every 
In others, 
either Di- 
ran in ever 
are fomed 
ir is tobe 
hem, that 
in Apple, 
ill rather 
Book IH. of Trunks. 
athwart one another; almoft like a Bend, or fometimes, an entire 
orbroken Saltyr in an Efeutcheon, In Oak, they make rather certain 
Columns, in the pofture of the Pale. And in El», they make, as it 38. 
were, many croft Parcels, inthe pofture of the Feß. 
26. $. This great difference in the Size and Pofítion of the Aer- 
Vefils, in the fame individual Plant, is one ground, for which, I think 
it probable, That there are divers Kinds of Aer Vefiils, as well as of 
Sap-Veffels. Even asin Animals, there are divers Kinds of Organs for 
Spiration, and the feparation of Aer: Fifhes having their Branchie ; 
Land-Animals their Lungs; and thofe in Frogs, Gc. being of a fome- 
what peculiar Kind, 
27. $. THE Form and Texture of thefe Veféls, and the various 
ways whereby they may be belt obferved, 1 have already deferibed 
and fhewed in my Anatomy of Roots. As to their Form, one thing P. i.e. 4. 
remarqued was this; That they are never Ramified, but diltindly 
continued from one end of a Plant, fmall or great, to the other: 
as the Nerves are in Animals. A further and cafie proof whereof, 
may be made, only by holding up a piece of an ordinary Cane, 
about 3 foot long, cut very {mooth at both ends, againft a full 
light + whereupon, if you keep it in a ftraight Live betwixt the 
Light, and the calt of your Eye, and then look [teadily, you may 
fee quite through it, that is, through the Aer-Vefels, which run ftraight 
along the Cave from end to end. 
28. $. As to their Textures whereas, oftentimes, the Aer Veffels 
appear to be wzroaved in the form of a very fmall Plate, it is to be 
noted, That it is not only of different bredth, in divers Plants, and 
ufually much broader in the Roof, than in the Trurk: but alfo, that 
in the Trunk, many times, the faid Veféls are unroaved or relolved, 
not inthe form ef a Plate, but of a Round-Thred. The Caufes of 
which Diverfity, are icapally Three; viz. The Wefiage of the 
Fibres of which the Aer-Veffels confit; The deference betwixt the 
faid Fibres, or betwixt the Warp and the Woof 5 And the different 
© Kinds of Woof. 
29. $. By the Weftage of the Fibres, it is, That the Veffels, of 
tentimes, wnroave in the form of a Plate, Asif we fhould imagine a 
piece of fine narrow Ribband, to be woun'd fpirally, and Edg to Edg, 
round about a Stick ; and fo, the Stick being drawn out, the R#b- 
band to be left in the Figure of a Tube, anfwerable to an Aer-Veffel, 
For that which, upon the w#roaving of the Veffil, feems to be a Plate, Tab. 39: 
or one fingle Piece, is, as it were, a Natural Ribband, confilting of 
feveral Pieces, that is, a certain number of Threds or Round Fibres, 
ftanding parallel, asthe Threds do in an Artificial Ribband. “And as 
ina Ribband, fo here, the Fibres which make the Warp, and which are 
Spirally continw'd 5 although they run parallel, yet are not coallefcents 
but conteined together, by other Tranfverfe Fibres in the place of 
a Woof. 
30. $. Andas the faid Fibres are tranfverfly continued, thereby 
making a Warp and Woof : So are they (as in divers woven Mann- 
fadures ) of very different Bulk 5 thole of the Former, being much 
bigger, and therefore much ftronger, than thofe of the Latter. By 
which means, as Cloth or silk will often Tear one way, and not ano- 
ther 5 fo here, while the Warp or thofe Fibres which are Spirally con- 
tinued; 
Tab. 33. 
