little: Whereas if we put other Herbs, or little Branches of the like Trees upon the brim of the Veffel, without touching the Water, they will wither and dry up in a little time. If we take a fmall Onion or Chibol, the Shoots of which come immediately from the bulb of the Root, and foak in Water the longeft of the exterior Shoots at their extremities, letting thofe that are in the middle, and the bulb not touch the Water, they will continue above fifteen Days extremely green; and I have known them grow in length above four Inches in four or five Days; but if any of the Shoots of another fmall Chibol like the former does not foak in the Water, thofe in the middle will attract but very little Juice from the bulb of the Root, and for this Reason they will grow but very little, and both will wither in three or four Days; which evidently fhews that the Ends or Shoots of the Chibol, which foak in the Water, convey it from the middle, (which denotes a kind of Circulation) and that the Leaves of other Herbs, and the Branches of Trees, carry the Water which they touch into the Canals and their Stalks, whence it is communicated to the Root and other Branches when they have occafion for it.

To confirm this Opinion of the return of the Sap to the Roots of Trees, I made the following Experiment.

In a very high Row of Hornbeam, fome of which joined each other at the Bark, we took two of thefe Trees, the Stalks of which were of the bigness of a Man's Arm; we fawed the Stalk of one of them about a foot and half below that place where the Barks united, and to hinder the Sap, rifing from the Root, from re

M 4

joining

joining the parts that were cut off, we put between them a little flat Stone; this Operation was made in the beginning of the Month of February. In the Spring following the fide Branches which were below the joining of the Stalks, threw out little Shoots and Leaves, as well as thofe which were above it, particularly one an Inch thick, which was half a Foot above the Incifion, and about a Foot and half below the joining: It caft out alfo new Shoots and Leaves from the Sap of Auguft, and from the Sap of the Spring following, in the fame manner as if it had received its nourishment from the Root; which can no otherwife be accounted for than by fuppofing that the Sap which rofe from the other Tree, paffed into the Bark of that which was cut, and being there preffed, defcended to the bottom of the cut Stalk or Trunk, whence it flowed back into the fide Branches. You have feen, Sir, the fuccefs of this Experiment as well as my felf, and you were pleafed to take care it fhould be made with the utmost exactness.

I have likewife oftentimes obferved, that if we cover with a very clear Glafs-bell the young Plants of Melons that are raised in a hot-bed, we fee, when the Sun is very hot, drops of Dew fticking to the extremities of the Leaves, which remain very green and firm; but if we take off the Bell there is no longer any Dew, and the Leaves wither a little, though they are no more heated than before, because they have no longer the hot Vapours of the Dung, and the Wind cools them; which is a proof that they fucked up this Dew before, and that it paffed into their little Canals to nourish them, the juice drawn

from

from the Root being not then fufficient to hinder them from withering.

If we foak in Water one Plant of Celandine cut off near the Earth, at the end where the Leaves are, and another cut, after the same manner, at the end which is cut, we fhall fee five or fix hours after iffue out in great abundance, yellow Juice from the fibrous Canals of that which touched the Water with its Leaves, after cutting the Stalk below the Leaves, but this Juice will not be much coloured; whereas that of the other, the cut end of which foaked in the Water will be very much coloured, and of a very fmall quantity, if we cut it after the fame manner; which cou'd not be if the Leaves which touch the Water did not partake of it to carry it into the Canals where the yellow Juice was; and if they did not take more of it than the end of the Stalk which was alfo foaked in the Water.

By thefe Experiments we may be convinced of the neceffity of the Dew, efpecially in hot Countries, as Egypt, where it very rarely Rains, and where the Earth which touches the Roots of Plants, continues oftentimes very dry; for to make amends for that inconveniency, there fall great Dews in Summer, the Drops of which, fucked in by the Leaves and Stalks of Herbs, ferve to feed them till the Rain comes. Thus we fee on almost all Plants, little points or filaments which make them look hairy, and are apparently fo many little Tubes to fuck in the Dew and Rain; for aquatick Herbs, as the Watercrefs, Brooklime, Potamogeton, Nenuphar or Water Lilly, &c. have their Stalks and Leaves fmooth and fhining, and none of these little Points; neither have they any occafion for them,

because

because their Roots are always in the Water. Nor has Sorrel any of thefe little exterior Filaments, because its Root runs deep into the Earth where it finds fufficient Moisture.

It is not enough that there is Sap fufficient to nourish Plants, but they alfo ftand in need of being immediately cheared by the light of the Sun, as we find by this Experiment.

Cover with a clear and narrow Glafs the Earth where Purflain and Lettice has been fown, they will open them felves as they come out of the Earth, if the Sun fhines upon the Glafs, and grow alfo very well, or better than if they were expofed to the open Air; but if you put a Pot full of Earth, where these Seeds have been fown, near a Stove, or in any other very hot place, tho' in a large and very light Room, thefe Seeds will rife in very loofe filamina three or four Inches high, with two very small Leaves on the top, which do not any wife enlarge themselves, and will die away in a little time, as do alfo thofe which are covered with an earthen Bell in the Sun: Whence it follows, that they do not die through want of Air, but of the immediate Light of the Sun. One might try whether by putting this fame Pot at a certain diftance from a great Flame in a clofe Place, thefe Seeds would thrive any better than by a heat without light.

To know how the Fruits and Seeds of Plants are brought to their maturity, we muft obferve and confider a great many things. The manner which appears to me the easiest of Explication is this.

The Roots and Leaves of Plants fuck up a great deal of Water, and this Water contains very little of the other Principles of Plants; and

because

because Water eafily evaporates, and the other Principles with difficulty, they continue engaged in the Pores and Fibres of Plants, and there mix and unite themselves differently according to the particular difpofition of each Plant.

There evaporates a great deal of Water every Day, especially when the Weather is hot; for from a fhoot of a Vine of a Foot long there daily evaporates above two or three Spoonfuls, which we may be convinced of when Vines congeal in the Month of May; for two hours after Sun rife their Shoots are black and dry, whence it follows, that in two hours the Sun caufes all the Water to evaporate, and that in twelve hours it would diffipate fix times as much; but though it lofes a great deal of this watery Juice, there returns enough to nourish the Plants, and always carry thither a few of the active Principles, till at laft there is enough to caufe a hardnefs and folidity in the Branches, and the Juice of the Fruits be proper for the nourishment of Animals; and if moreover there is too much Water after the Fruit is gathered; this furplus. diffipates it felf in a little time, and the Fruit remains in its perfect maturity, though there continues a great deal of Water.

Plants that laft but one Year, as fennel, Poppies, &c. grow at laft very hard, and the Pores through which the external Water entered fhut themselves up, and the Sun continuing to dry them, there remains a great quantity of the earthy, faline, and oily Parts, perfectly mixed with fome parts of Water there retained and inclofed, and which with great difficulty difengage themselves from them.

The fame thing happens to Grains and Seeds, for at laft they grow fat and oily, because the

watery