6 
The vegetable SYSTEM. 
fea-weed, foot, and rags, and many more are inflances : all of 
which yet in a certain proportion, ferment and break tough Earths, 
and render them more fit for Vegetation. 
No Plant can grow without Earth, for that mufl: make its fub- 
ibance : fuch Earth as water can diUblve moll ealily, anfwers this 
purpofe beft ; and others in proportion as art and induftry bring 
them nearer to this ftate. We are not to fuppofe Plants feed on any 
thing elfe : thofe which live in water are certainly fed by the Earth 
contained in that water ; thofe upon rocks, by dull blown into their 
crevices and wafhed down by rains ; thofe upon walls, by the mould 
among the mortar ; and even thofe on dunghills, by the Earth 
mixed among the mafs ; for abfolute dung will not fupport any Plant 
beyond a little fungus. 
CHAP. IV. 
Of the Effects of Water in Vegetation. 
EAT itfelf is not more immediately neceffary to Vegetation 
than Water. Tho’ earth is the food of Plants; it is Water 
which conveys this to their feveral parts. This enters the Roots, 
carrying with it a certain quantity of the earth, which it leaves 
behind in the Plant to encreafe its folid fubflance, itfelf evaporating 
through the leaves. Dry earth, in ever fo fmall particles, could not be 
received into the velTels ; nor if received, could it pafs through them. 
There is necefiity of a Fluid to give it entrance and conveyance; and 
the Fluid nature furnilhes is Water. Rains give this to the earth, 
and it is detained at a fmall depth beneath the furface, where the 
Roots run : the air alfo abounds with it : fo that the Plant is fup- 
plied by day, one of thefc ways, and during night the other ; and 
cannot but receive it. 
A CERTAIN proportion of Moifture is alfo neceffary, for the health 
of the Plant, to be retained always within its Veffels. This Moi- 
fture is not pure Water, for it is the Juice of the Herb ; but it was 
Water firft, and as it wafles muft be fupplied by Water. The fun 
exhales 
