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health. As aifo how abfurd that common practice 
Is, of feeding down Wheat in the winter and fpring 
with ftieep •, for by fo doing, the ftalks are rendered 
very weak, and the ears are in proportion (barter * 
nor are the grains of Corn fo plump and well nou- 
riflied, as that which is not fed down upon the fame 
ground t this is a fact which I can affert from many 
years experience •, for when Corn or Grafs is fed 
down clofe to the root, the fucceeding blades will 
be much finer than if the firft Leaves had been left 
remaining ; which is evident from all fheep paftures, 
where the Grafs is much finer and fhorter than in 
other places ; as alfo upon lawns and bowling-greens, 
where the Grafs is often mowed, the blades will be 
rendered finer in proportion to the frequency of mow- 
ing it, yet the fpecies of Grafs is the fame with that 
on the richeft paftures •, fo that although this may be 
a defirabie thing for lawns, &c. in gardens, yet 
where regard is had to the produce, this fliould be 
avoided. 
Befides thefe, there are other ufes for which Leaves 
are defigned, one of which is that of fhading the buds 
for the future fhoots from the fun, which would ex- 
hale and dry up all their moifture, as alfo the fhading 
of the young fruit, which is abfolutely neceffary du- 
ring the time of their growth ; for I have fufpended 
the Leaves of trees which were growing againft walls, 
fo as to expofe the fruit to the fun, and not taken 
any of them off the branches, yet I have always found 
thofe fruits fo expofed, have been greatly (tinted in 
their growth, and have never arrived to near the 
fize of others above and below them on the fame 
branches, nor were they fo well tailed, or replete 
with juice. 
In making this experiment, I was as careful as pof- 
fible not to reverfe the furfaces of the Leaves, having 
been thoroughly convinced, from many repeated ex- 
periments, how prejudicial that is to all plants ; but 
notwithftanding this precaution, the event was as be- 
fore-mentioned. 
Another principal ufe of the Leaves is to throw off 
by tranipiration, what is unneceffary for the growth 
of the plants, anfwering to the difcharge made by 
fweat in animal bodies ; and as plants receive and 
tranfpire much more, in equal time than large ani- 
mals, fo it appears how neceffary the Leaves are to 
preferve the plants in perfeft health ; for it has been 
found by the mod; exadt calculations, made from re- 
peated experiments, that a plant of the Sun-fiower re- 
ceives and perfpires, in twenty-four hours, feventeen 
times more than a man. 
As naturalifts have generally afcribed a four-fold ufe 
to Leaves, I fhall beg leave to mention them here, 
and then fliall give an account of the mod accurate 
experiments which have been made to afcertain the 
truth of their hypothefes. 
1. Chiefly, that they do in the fpring time receive 
the crude humours into themfelves, divide them very 
minutely, and move them (trongly in the utricles, and 
perhaps draw in from the air what is neceffary, though 
unknown to us, and carry back great plenty of elabo- 
rate juice to the plant. 
2. That there may be a tranipiration of what is un- 
profitable, anfwering to the difcharge made by fweat ; 
for fometimes thofe excretory veffels of the Leaves are 
fo overcharged by the great plenty of diftending hu- 
mour [ ]uice,] that they burft in the middle, and let 
go the more fubtile parts ; nor is it feldom, that, in a 
hot feafon, great plenty of juices are this way dis- 
charged and imbibed. Thus Manna is found to ex- 
fade [fweat forth] from the Leaves of certain trees, if 
a cold night (hould follow a hot day ; and the fame 
thing frequently happens in divers other plants and 
trees, as we learn from the bees flying to the Lime- 
tree, that they may gather that gumous fubftance from 
their Leaves ; and it is from the furfaces of the 
Leaves, as well as from the flowers, thofe animals 
colled their honey •, but if the heat fhould be lefs, 
all the fuperfliiQUs humours, except thofe which, per- 
haps, are tranfmitted by infenfible tranfpiration thro’ 
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the arterial veffels, exhaling naturally, are feen to re- 
turn into the trunk. 
3. That the bibulous veffels, dried by the diurnal 
heat, and for this reafon to be compared to veins, 
may imbibe, in the night-time efpecially, thofe wa- 
tery parts, which, among others, lie hid in the air 
under the form of a very thin dew, and fo make 
amends for the lofs made by the arteries, by the new 
moifture received. 
% Laftly, the Leaf ferves chiefly for this purpofe, 
that it may keep and nourifh the eye, or gem, until 
the gem, by degrees growing out to a greater bulk, 
preffes together the veffels of the foot-ftalk, from 
whence the humour is by little and little flopped in 
the Leaf, till it cannot any more return to the foot- 
llalk •, which, by the ceafing of the afflux and reflux 
of the nutritive juice, grows putrid, whence a con- 
fumption being caufed, the Leaf dies, and falls off, 
which is the chief caufe of the falling of the Leaves 
in autumn. 
The Rev. Dr. Hales, in his excellent Treatife of Ve- 
getable Statics, (peaking of the perforation of plants, 
gives an account of the following experiments, viz. 
That in July or Auguft he cut off feveral branches of 
Apple-trees, Cherry-trees, Pear-trees, and Apricot- 
trees, two of a fort ; they were of feveral fizes, from 
three to fixfeet long,withproportionallateralbranches, 
and the tranfverfe cut of the largeft part of the ftems 
was about an inch diameter. 
That he ftripped off the Leaves of one bough of each 
fort, and then let their ftems in feveral glaffes, pour- 
ing in known quantities of water. 
The boughs with Leaves on them imbibed fome fif- 
teen ounces, fome twenty, twenty-five, or thirty, in 
twelve hours day, more or lefs, in proportion to the 
quantity of Leaves they had, and when he weighed 
them at night, they were lighter than in the morning. 
While thofe without Leaves imbibed but one ounce, 
and were heavier in the evening than in the morning, 
they having perfpired little. 
The quantity imbibed by thofe with Leaves de- 
creafed very much every day, the fap-vefiels being 
probably Ihrunk at the tranfverfe cut, and too much 
faturate with water, to let any more pafs, fo that ufu- 
ally in four or five days the Leaves faded and wi- 
thered much. 
He adds, that he repeated the fame experiments 
with Elm branches. Oak, Ofier, Willow, Sallow, 
Afpen, Currant, Gooleberry, and Filbert branches, 
but none of thefe imbibed fo much as the forego- 
ing, and feveral forts of Evergreens very much lefs. 
He adds alfo another experiment : That on the 1 5th 
of Auguft, he cut off a large Pippin with two inches 
Item, and its twelve adjoining Leaves : that he 
fet the ftem in a little phial of water, which im- 
bibed and perfpired in three days one third of an 
ounce. 
And that at the fame time he cut off from the fame 
tree another bearing twig of the fame length, with 
twelve Leaves, no Apple on it, which imbibed in 
the fame three days near three-fourths of an ounce. 
That about the fame time, he fet in a phial of water 
a fhort ftem of the fame tree, with two large Apples 
on it, without leaves, and they imbibed near three- 
fourths of an ounce in two days. 
So in this experiment, the Apples and Leaves im- 
bibed four-fifths of an ounce, the Leaves alone near 
three-fifths, but the two large Apples imbibed and 
perfpired but one third part fo much as the twelve 
Leaves, then the one Apple imbibed the one-fixth 
part of what was imbibed by the twelve Leaves ; 
therefore two Leaves imbibe and perfpire as much 
as one Apple ; whence their perfpirations feem to 
be proportinable to their furfaces, the furface of the 
Apple being nearly equal to the fum of the upper 
and under furfaces of the two Leaves. 
Whence it is probable that the ufe of thefe Leaves 
(which are placed juft where the fruit joins to the 
tree) is to bring nourifliment to the fruit. 
And 
