(ay) 
consistency and odour. Ifa plant be placed in a 
cellar, into which is admitted a small portion of 
light through a window or cranny, thither the plant 
directs its growtb, and even acquires an unnatural 
length in its attempt to reach it.(1) These facts:ad- 
mitted, no one can doubt the agency of light in ve- 
getation; but in relation to this’ agency, various 
opinions exist; one, that light enters vegetable mat- 
ter and combines with it ; another, that it makes no 
part either of the vegetable or of its aliment, but 
directly influences substances which are alimenta- 
ry ;(2) and a third, that ‘besides the last effect, it 
stimulates the organs of plants to the exercise of 
their natural functions.(3) 
Without doing more than state these opinions, 
we proceed to offer the results of many experiments 
on this subject. Ist. That tn the dark, no oxigen 
is produced, nor any carbonic acid obscrbed ;' on 
the contrary, oxigen is absorbed and carbonic acid 
produced. 2d. That plants exposed to light, pro- 
duce oxigen gas in water. 3d. That light is‘essen- 
tial to vegetable transpiration ; as this process never 
takes place during the night, but is copious during 
the day; arid 4th. That plants raised in the dark 
abound in watery and saccharine juices—but are 
deficient in woody fibre, oi] and resins; whence it 
is concluded, that saccharine compounds are form- 
ed in the night, and oil, resins, &c. inthe day. 
“ (1) It is by a knowledge of this fact, that gardeners bleach chi¢ory and cellérr, 
&c. 
(2) See Fourcroy, vol. viii. 
(3) See Chaptal on vegetation. 
