336 
THE LADIES’ MAGAZINE OF GARDENING. 
portion of oxygen of which the former process had deprived it. The 
former process, carried on by the agency of the oxygen gas of the air, 
was essential to living action, and affected the well-being of the whole 
plant: that exercised by the agency of light is not necessary to life; is 
local, not general in its operation; and is capable of proceeding in circum¬ 
stances and under conditions incompatible with living action. By with¬ 
drawing the air altogether, or depriving it of oxygen gas, vegetation soon 
ceases through the whole plant; but the exclusion of light from any 
part of the plant affects that part only; and even the total exclusion of 
that agent only deprives the plant of certain properties necessary to its 
perfection, but not essential to its life. These differences in the processes 
by which oxygen gas is alternately consumed and evolved, during the 
vegetation of plants in sunshine, are so manifest, both in their nature and 
effects, as to justify the ascription of a name to the latter process distinct 
from that given to the former. It might, perhaps, be denominated the 
chemical process, in contradistinction to that named physiological. 
It would contribute much, we think, to simplify our inquiries concern¬ 
ing vegetation, to bear in mind these distinctions: to consider the one 
process as accomplished by the agency of the air, and essential to the life 
and growth of the plant; the other, as subordinate, depending on the 
agency of light, and though necessary to the perfection of vegetation, yet 
not essential to its existence. In this manner, each process may be 
followed out separately, both in regard to its immediate effects and remote 
consequences, without clashing with the other; and the apparently 
discordant and even contradictory phenomena which, on a first view, they 
seem to exhibit, may be reconciled, and considered, not less in theory 
than in fact, as conspiring together to form one harmonious and perfect 
whole. 
Applying these views to the subject under consideration, we see no 
difficulty in comprehending how the same identical volume of air in the 
plant-case of Mr. Ward, should, for so long a period, serve the purposes 
of vegetation, without becoming foul from within, or receiving or 
requiring renewal from without. The experiments of De Saussure 
furnish, as we have seen, examples of a similar kind, and supply, at the 
same time, the desired explanation. The daily depravation and subse¬ 
quent purification which the air underwent in the glass vessels of that 
eminent chemist, must be equally accomplished, under similar circum¬ 
stances, in the glass cases of Mr. Ward, that is, when their plants are 
similarly exposed to vegetate alternately in sunshine and in shade. And 
as the former found the air to continue for many days together unchanged, 
either in purity or in volume, when so treated, so must the air in the 
