Mr. Cavennisu’s Experiments on Air. r49 
water, they feem to be reduced almoft intirely to water. and 
thofe two kinds of air. Now plants growing in water without 
earth, can receive nourifhment’ only from the water and air, 
and muft therefore in all probability abforb their phlogifton 
from the water. It is known alfo that plants growing in the 
dark do not thrive well, and grow in a very different manner 
from what they do when expofed to the light. 
From what has been faid, it feems likely that the ufe of rite 
in promoting the growth of plants and the produdtion of 
dephlogifticated air from them, is, that it enables them to 
abforb phlogifton from the water. To this it may perhaps be 
objected, that though plants do not thrive well in the dark, yet 
‘they do grow, and fhould therefore, according to this hypo- 
thefis, abforb water from the atmofphere, and yield dephlo- 
gifticated air, which they have not been found to do. But we 
have no proof that they grew at all in any of thofe cafes in 
which they were found not to yield dephlogifticated air; for 
though they will grow in the dark, yet their vegetative pow- 
ers may perhaps at firft be intirely checked by it, efpecially 
confidering the unnatural fituation in which they muft be 
placed in fuch experiments. Perhaps too plants growing in 
the dark may be able to abforb phlogifton from water not 
much impregnated with dephlogifticated air, but not from 
water ftrongly impregnated with it; and confequently, when 
kept under water in the dark, may perhaps at firft yield fome 
dephlogifticated air, which, inftead of rifing to the furface, 
may be abforbed by the water, and, before the water is fo 
much impregnated as to fuffer any to efcape, the plant may 
ceafe to vegetate, unlefs the water is changed. Unlefs there- 
fore it could be fhewn that plants growing in the dark, in 
water alone, will increafe in fize, without yielding dephlo- 
gifticated 
