109 
x 
shade ; for oxygen gas is alike necessary in both si* 
tuations, and is in a similar manner converted into 
carbonic acid. Under direct exposure to the solar 
rays, however, this acid gas is again decomposed., 
and its oxygen is restored to the atmosphere ; while^ 
in the shade, no such operation takes place, and the 
air, therefore, remains permanently depraved. 
350. But farther, it also appears, that the production 
of oxygen is entirely confined to the leaves (292.) and 
other green parts of plants ; and that the flowers^ 
the fruits, the stems and roots of vegetables (279.) 
both in sunshine and in the shade, convert always 
the oxygen gas of the air into carbonic acid. Since, 
likewise, the leaves acquire their green colour by 
the direct influence of the same agent as occasions 
the development of oxygen, may we not reasonably 
presume, that some necessary connection obtains be- 
tween the production of that gas and the formation 
of this colour ? Let us then pursue these inquiries a 
little farther, and try to discover the nature of that 
relation which appears to subsist between the pro- 
duction of oxygen gas, and the formation of the green 
colour in plants. 
SECT. III. Of the Relation subsisting between the produce 
tion of Oxygen Gas, and the formation of the Colours of 
Plants. 
351. SINCE, from the conclusions deduced in the 
foregoing section, it appears, that the pure air fur- 
