Mr. Papin shews, that Air will pass in at the Leaves, and out thro’ the Plant at the Roots, but Water will not pass in at the Leaves; and that if the Leaves have no Air, a Plant will die; but if the Leaves have Air, tho’ the Root remain in Water in vacuo, the Plant will live and grow.
Dr. Grew, in his Anatomy of Plants, mentions Vessels, which he calls, Net-work, Cobweb, Skeins of Silk, &c. but above all, the Multitude of Air-Bladders in them, which I take to be of the same Use in Leaves, as the Vesiculæ are in Lungs. Leaves being as Lungs inverted, and of a broad and thin Form; their Vesiculæ are in Contact with the free open Air, and therefore have no need of Trachea, or Bronchia, nor of Respiration.
CHAP. II.
Of Food of Plants.
The chief Art of an Husbandman is to feed Plants to the best Advantage; but how shall he do that, unless he knows what is their Food? By Food is meant that Matter, which, being added and united to the first Stamina of Plants, or Plantulæ, which were made in little at the Creation, gives them, or rather is their Increase.
’Tis agreed, that all the following Materials contribute, in some manner, to the Increase of Plants; but ’tis disputed which of them is that very Increase or Food. 1. Nitre. 2. Water. 3. Air. 4. Fire. 5. Earth.
I will not mention, as a Food, that acid Spirit of the Air, so much talk’d of; since by its eating asunder Iron Bars it appears too much of the Nature of Aqua Fortis, to be a welcome Guest alone to the tender Vessels of the Roots of Plants.
Nitre is useful to divide and prepare the Food, and may be said to nourish Vegetables in much the same Manner as my Knife nourishes me, by cutting and dividing my Meat: But when Nitre is apply’d to the Root of a Plant, it will kill it as certainly as a Knife misapply’d will kill a Man: Which proves, that Nitre is, in respect of Nourishment, just as much the Food of Plants, as White Arsenick is the Food of Rats. And the same may be said of Salts.
Water, from Van-Helmont’s Experiment, was by some great Philosophers thought to be it. But these were deceived, in not observing, that Water has always in its Intervals a Charge of Earth, from which no Art can free it. This Hypothesis having been fully confuted by Dr. Woodward, no body has, that I know of, maintain’d it since: And to the Doctor’s Arguments I shall add more in the Article of Air.
Air, because its Spring, &c. is as necessary to the Life of Vegetables, as the Vehicle of Water is; some modern Virtuosi have affirm’d, from the same and worse Arguments than those of the Water-Philosophers, that Air is the Food of Plants. Mr. Bradley being the chief, if not only Author, who has publish’d this Phantasy, which at present seems to get Ground, ’tis fit he should be answer’d: And this will be easily done, if I can shew, that he has answer’d this his own Opinion, by some or all of his own Arguments.
His first is, that of Helmont, and is thus related in Mr. Bradley’s general Treatise of Husbandry and Gardening, Vol. I. p. 36. ‘Who dry’d Two hundred Pounds of Earth, and planted a Willow of Five Pounds Weight in it, which he water’d with Rain, or distill’d Water; and to secure it from any other Earth getting in, he covered it with a perforated Tin Cover. Five Years after, weighing the Tree, with all the Leaves it had borne in that Time, he found it to weigh One hundred Sixty-nine Pounds Three Ounces; but the Earth was only diminish’d about two Ounces in its Weight.’