The Roots of some Plants grow more thin and slender, as they enter deeper into the ground, and end in a Cone or slender Point, as the Roots of Trees. But the Roots of other Vegetables swell in∣to a round Root, as Turneps, Tulips, Onions, &c.
The Reason why the Roots of Trees, and most other Vegetables are slender towards the ends, is because the Juice passing through them, is carri∣ed upwards, and abides longer in the upper part of the Plants; for tho' the heat, by the virtue whereof Nutrition is performed, doth extend it self into all parts, and be carried upwards and downwards, yet it is certain, that it is always more strongly conveyed to the upper parts, than to∣wards the lower; and therefore seeing that the upper part of Trees doth receive more nourishment, and is longer nourished, it is no wonder if be also bigger and larger, and that the Roots end in a point. But the Roots of Turneps, &c. are Round, because their nourishment is received into the first joint of them, which consisting of several entang∣led parts, and being endued with narrow pores, the nourishment cannot freely pass or be strained through them, and therefore it is necessary that the said matter be diffused sideways, and that the Fibres which are big and swell'd with juice, spread and enlarge themselves.
IV. The Com∣pression of the Earth makes the Roots to grow the faster. If an Herb be cut up by the Roots, and put again into the Earth, and the same be strongly bea∣ten down, and this about the beginning of Winter, the Roots will be found extreamly encreased the following Summer.
The Reason is, because moisture having by this means been hindred from entring into the inward parts of the Plant, doth the longer continue in the Root, and dilate the same. And therefore it is common with Gardners after they have sowed Onions and Turneps, to press down the loose Earth round about them with Rowlers or the like.
V. Why the Stalks of some Herbs are hollow▪ Some Plants have hollow Stalks, as all sorts of Reeds, and the Straw of Corn, but with joints.
The Reason is, because the Fibres which serve to convey the nourishment, are not derived from the Pith of the Plant, but from the sides of the budding Knot; which because they withdraw from the middle, and observe a certain distance, do leave a certain space there, and produce a Cavity. Hence it is that in Onions the Pipe is larger about the midst, because the ends of the Fibres spread further from one another, and affect a spherical Figure. For the several Coats of Onions are like so many Leaves, which being broader about the midst, are roll'd together like the surface of a Cy∣linder.
VI. Why the Bodies of Trees are round. Almost all the Bodies or Trunks of Trees have the same Figure, viz. a round one, tho' they dif∣fer in length, and other manifold varieties.
The Reason of the roundness of the Trunks of Trees, is the same with that of the Roundness of the drops of Liquid Bodies. For as the Coelestial Globuli, by their equal pressing of the parts of water towards their Center, do make them spheri∣cal; so the same Globuli, by dashing against the outside of Trees, drive the same to a Roundness. And tho' Plants be much inferiour in softness to Water, and therefore cannot be so readily figured by the surrounding subtil matter; yet this doth not hinder but that the same which is done, as it were in a moment, in the parts of Liquid Bodies,
may be done in a larger time, and with often rei∣terated attempts in harder Bodies. So we see that Iron Work which was rough before, becomes smooth'd and polish'd by frequent handling, or even rubbing against ones Cloaths.
VII. What is the reason of the hard∣ness of the Barks of Trees. The outward part of the Tree, and which covers it like a Shift, is wont to be harder than its inward Substance. Hence it is that most Trees shed their Bark in the Spring.
The hardness of the outside of Trees proceeds from other Bodies that dash against it. For there are innumerable little Bodies, not only of the 1st and 2d Element, but also particles of the 3d Element, which continually push and dash against the sur∣face thereof, and drive all the parts towards the midst. Thus our Hands and Feet by the impulse of other Bodies, do contract a brawny hardness; likewise so the Crust of Bread, and the surface of Roastmeat, grows hard by the heat of the Fire acting upon it, and much compacter than the in∣ward substance. The reason why Trees in the Spring do lose their Barks, is, because the copious affluence of the alimental moisture, being at that time in greater abundance betwixt the Trunk and the Bark, doth loosen the Glew wherewith they were fastned together.
VIII. The Ali∣ment of Trees is not only trans∣mitted through the Pith, nor only be∣tween the Bark and the Wood. But for all this, we are not to suppose with some, that all the nourishment of Trees is conveyed be∣twixt the Bark and the Wood; or, which is the opinion of others, through the Pith only, but ra∣ther both ways; tho' indeed nothing hinders but there may be a mutual communication or irrora∣tion of both these ways with each other. Foras∣much as we see there are some Trees which live and grow, when their Pith is quite consumed, as Wallnut, Willow, &c. as on the other hand there be Trees which grow after that their Barks are ta∣ken from them.
IX. What is the cause of the great variety of the Leaves of Plants. Almost all the Leaves of Plants differ, and are of different Figures. For some are large and broad, as those of a Gourd; others small and slender like Hair, as the Pine Tree; and some thick and fleshy, as in Purslain, &c.
The conformation of the Leaves is caused by the different texture of the Fibres, which as they do diversly meet together, and become entangled, or else separate from one another, so they form Leaves of different shape and figure. For tho' the Leaves of all Plants consist of the same parts as their Branches and Trunk doth (because the thin Skin of the Leaf is nothing else but the enlargement of the thin Skin of the Branch, which partly by the occasion of new parts, and partly by the extension of its former parts becomes spread into that breadth) yet do they receive their figure from the various disposition of the Fibres. Hence it is that some Leaves are long because their Fibres lie only stretched out in length, others round, when the Fibres display themselves more winding and turning, and so for the rest. For seeing that most of them derive their original not from the Bark alone, but from the inward substance, so it is that Alimen∣tary Juice is differently suck'd and strain'd, ac∣cording to the disposition of the Navel Knot of the Tree, whence the diversity of the Fibres, and of the figure of the Leaves doth arise.
X. Of the dif∣ferent Leaves of Plants. Hence it is that some Plants have long and slen∣der Leaves, as the Willow; others bent and crook∣ed, like Orris; others round and hollow, like Na∣velwart;