f 994 7. 
4. Do you fuppofe that plants draw the wholé, or 
any part, of their nourifbment from air? 
I believe, if they receive air into their conftitution 
at all, itis by the root, and that, I think, is probable; 
yet the organization may, by a kind of natural che- 
miftry, fo change its abforbed nourithment, as to 
render the actual admiflion of common air doubtful. 
5- Do you fuppofe that the earth, when fallowed, 
attracts any fubjtance from the air, favourable to 
vegetation? 
In fome cafes fallows acquire an accumulation of 
decayed leaves, &c.; in others, they are better pul- 
verized by froft, &c. than by culture; but I fufpect 
they imbibe no fubftance from the air. 
6. Do you fuppofe that roots, as turnips, potatoes, 
&Sc. extract nourifhment from the air by their Stems or 
leaves, and hence exhauft the foil lefs than grain? Or 
do they fertilize land by the fubjtances they throw off; 
and leave behind them? 
As far as air is a medium for light and humidity, 
they may; but I think not from the air itfelf; and 
the greater proportion of foliage, the more benefit 
perhaps from light and aqueous vapour; but I am 
difqualified for explaining how thefe plants improve 
the foil, unlefs by their decayed leaves and ftalks. 
7. Do you fuppofe that trees draw any nourifbment 
from the air, by their leaves? 
I do not, excepting air as a medium for communi- 
cating light, warmth, and humidity. 
(8. Do ' 
