But Wheat, being a terrestrial Plant, (tho’ in Winter it will live many Days under Water, whilst the slow Motion of its Sap gives it little or no Increase), requires a free open Air, and does not succeed so well in low sheltery Places, as upon higher and opener Situations; where the Air has a greater Motion, and can more easily carry off the Recrements from the Leaves, after it has shaken off the Dews and Rains, which would otherwise suffocate the Plants; and therefore the Leaves are made so susceptible of Motion from the Air, which frees them from the Dews, that would stop in the Recrements at the _Vesiculæ_ of the Leaves, but shaken down will nourish the Plants at the Roots: The want of this Motion weakening the Wheat, ’tis (as Animals in the like sickly Case are) the more unable to stand, and the more liable to be press’d down by the Weight of Rain-water, and more unable to rise up again when down: All which Evils are remov’d by the free Motion of the Air, which shakes off both Dews and Rains, and thus contributes to prevent the falling (or lodging) of Wheat. A great Quantity also of the Sun’s Rays is necessary to keep Wheat strong, and in Health; and in _Egypt_, and other hot Countries, it is not so apt to fall, as it is when sown in Northern Climates, tho’ the Produce of the South be the greatest[152]. [152] This proves that the Crop doth not lodge on account of its Bigness. It may be observ’d, that every Leaf is inserted into a Sort of Knot, which probably delivers the Sap to be depurated at the _Vesiculæ_ of the Leaves, and then receives it back again for the Nourishment of the Plant, doing for that Purpose the Office of an Heart: But the Sun with his Rays supplies the Part of Pulse, to keep the Sap in Motion, and carry on its Circulation, instead of the Heart’s _Systole_ and _Diastole_. Wheat, being doubtless originally a Native of a hot Country, requires by its Constitution a considerable Degree of Heat to bring it to Perfection; and if much of that Degree be wanting, the Wheat will be the weaker; and when the Solar Rays cannot reach the lower Parts of the Stalks, the lowest Leaves and Knots cannot do their Office; for which Reason the Chyle must mount higher before it be made into Sap, and there must be then a greater Mixture of crude Chyle next to the Ground, as by the white Colour it appears[153]. By this Means that Part, which, if it had a due Share of the Sun’s Influence, would be harden’d like a Bone or Spring, for the Support of the Stalks, for lack of that, becomes more like to a Cartilage, soft and weak, unable to sustain the Weight of the bending Ear, which, having its greatest _Impetus_ against this Part, which is most feeble to resist it, it yields, and lets it fall to the Ground; and then the Grain will be blighted.