4? 
ihe greater part of the oxygen is converted into this 
acid, a very small portion should still be retained by 
the plant* 
265. But, perhaps, some who admit the conver- 
sion of oxygen gas into carbonic aeid by plants grow- 
ing in the shade or in darkness, may still contend 
that this is not a perfect vegetation, because the di- 
rect influence of ligjit is withdrawn. We acknow- 
ledge the great influence of light in this process, but 
we have seen (25.) that it is not essential to it ; for 
plants live and grow in situations from which light is 
wholly excluded. All the experiments also> which 
we have heretofore detailed, both in this and in our 
former treatise, although they were not made under 
a direct exposure to the sun's rays, were conducted 
in open rooms where light had the freest access ; and 
the plants assumed all the characteristic properties 
and appearances, which were peculiar to them. It is, 
likewise, sufficiently evident, that, even in our own 
climate, and especially in high northern latitudes, a 
vast number of plants live and flourish in natural si- 
tuations, where the direct rays of the sun seldom or 
never penetrate 5 and yet, in such situations, they at- 
tain a state of perfect vegetation. How many hours, 
also, of our brightest days, and even how many en- 
tire days, are we deprived of the direct influence of 
the sun's rays, at the very season when vegetation is 
advancing with the greatest rapidity and vigour ? If> 
indeed, this direct influence were essential to vegeta- 
tion, many plants^ which we now behold, would 
never be produced at all, and all the tribes of vege- 
tables would experience such frequent and continued 
