And for Knots, they are so necessary, as to be seen not only where collateral Branches put forth; but in such Plants also as shoot up in one single Trunk; as in Corn; wherein, as they make for the strength of the Trunk; so by so many percolations as they are Knots, for the transmission of the Sap more and more refined towards the Ear. So that the two general uses of Knots are for firmer standing, and finer growth.
Lastly, as the due Formation and Nutrition of the Germen are provided for, so is its security also; which both in its position upon the Trunk, and that of its Parts among themselves may be observed. The position of its Parts shall be considered in speaking of the Leaf. As to its standing in the trunk, ’tis alwayes betwixt the trunk or Elder Branch, and the Basis of the Stalk of the Leaf; whereby it is not only guarded from the Injuries of any contingent Violence, but also from the more piercing assaults of the Cold, so long till in time ’tis grown, as larger, so more hardy. The manner and uses of the position of every Germen, considered as after it becomes a Branch, hath already been by the Ingenious Mr. Sharrock very well observed; to whom I refer.
Upon the prolongation of the Germen into a Branch, its Leaves are thus display’d. The Parts whereof are substantially the same with those of a Branch: For the Skin of the Leaf is only the ampliation of that of the Branch; being partly by the accretion of new, & partly the extention of its already existent parts (dilated as in making of Leaf-Gold) into its present breadth. The Fibres or Nerves dispersed through the Leaf, are only the Ramifications of the Branch’s Wood, or Lignous Body. The Parenchyma of the Leaf which lies betwixt the Nerves, and as in Gentlewomens Needle-works, fills all up, is nothing else but the continuations of the Cortical Body, or inner part of the Barque from the Branch into it self, as in most Plants with a fat Leaf, may easily be seen.
The Fibres of the Leaf neither shoot out of the Branch nor Trunk, nor stand in the Stalk, in an even Line; but alwayes in either an Angular or Circular posture, and usually making either a Triangle, or a Semi-Circle, or Cord of a Circle; as in Cycory, Endive, Cabbage, &c. may be observed: And if the Leaf have but one main Nerve, that also is postur’d in a Circular or Lunar Figure; as in Mint and others. The usual number of these Nerves or Fibres is 3, 5, or 7. See the Figures from 20, to 29.
The reason of the said Positions of the Fibres in the Stalk of the Leaf, is for its more erect growth, and greater strength; which, were the position of the said Fibres in an even Line, and so the Stalk it self, as well as the Leaf flat, must needs have been defective; as from what we have said of the Circumferential posture of the Lignous Body in the Trunk, we may better conceive.
As likewise for the security of its Sap: For by this means it is, that the several Fibres, and especially the main or middle Fibre of the Leaf, together with a considerable part of the Cortical Body, are so disposed of, as to jut out, not from its upper, but its back, or nether plain. Whence the whole Leaf, reclining backward, becomes a Canopy to them, defending them from those Injuries which from colder Blasts, or an hotter Sun, they might otherwise sustain. So that by a mutual benefit, as these give suck to all the Leaf, so that again protection to these.
These Fibres are likewise the immediate visible Cause of the shape of the Leaf: For if the nethermost Fibre or Fibres in the Stalk be in proportion greater, the Leaf is long, as in Endive, Cycory, and others: If all of a more equal size, it spreads rounder, as in Ivy, Doves-foot, Colts foot, &c. And although a Dock-Leaf be very long, whose Fibres notwithstanding, as they stand higher in the Stalk, are disposed into a Circle all of an equal size; yet herein a peculiar fibre, standing in the Center betwixt the rest, and running through the length of the Leaf, may be observed.
In correspondence also to the size and shape of these Fibres, is the Leaf flat: In that either they are very small, or if larger, yet they never make an entire Circle or Ring; but either half of one, as in Borage, or at most three parts of one, as in Mullen, may be seen. For if either they were so big, as to contain; or so entire, as perfectly to include a Pith, the Energy of the Sap in that Pith, would cause the said Lignous Ring to shoot forth on every side, as it doth in the Root or Trunk: But the said Fibres being not figur’d into an entire Ring, but so as to be open; on that hand therefore where open, they cannot shoot any thing directly from themselves, because there they have nothing to shoot; and the Sap having also a free vent through the said opening, against that part therefore which is thereunto opposite, it can have no force; and so neither will they shoot forth on that hand; and so will they consequently that way only which the force of the Sap directs, which is only on the right and left.
The several Fibres in the Stalk, are all inosculated in the Leaf, with very many Sub-divisions; according as these Fibres are inosculated near, or at, or shoot directly to the edge of the Leaf, is it even or scallop’d. Where these Inosculations are not made, there we have no Leaves, but only a company of Ramulets, as in Fennel.