98 LADIES 7 FLOWER GARDENER. 



The alternate action of vitiation and purification is emphatically 

 described as follows by Mr. Ellis, in the pamphlet before us : 

 " Under a bright sunshine, the two processes by which carbonic 

 acid is alternately formed and decomposed go on simultaneously ; 

 and their necessary operation, in as far as regards the condition 

 of the air, is that of counteracting each other. Hence, though 

 both may be continually exercised in favorable circumstances, the 

 effects of neither on the atmosphere can be ascertained by ordi 

 nary means ; and, consequently, though, in the experiments of 

 De Saussure with common air, the production and decomposition 

 of carbonic acid by plants in sunshine must have been continually 

 going on, yet, in all the analysis which he made, the air was 

 found unchanged, either in purity or volume ; in other words, the 

 processes of formation and decomposition of this acid gas exactly 

 counterbalanced each other. 



" Of the two processes which have now been described (con- 

 tinues our authority), each may be considered as in its nature and 

 purpose quite distinct from the other ; hence their efforts may be 

 readily distinguished ; neither do they necessarily interfere, when 

 actually working together. The first or deteriorating process, in 

 which oxygen gas is consumed, goes on at all times and in all 

 circumstances when vegetation is active. It requires always a 

 suitable temperature in which to display itself ; and when that 

 temperature falls below a certain point, which is very variable in 

 regard to different plants, the process is more or less completely 

 suspended, again to be renewed when the temperature shall re- 

 turn. This conversion of oxygen into carbonic acid is as neces- 

 sary to the evolution of the seed as to the growth of the plant, 

 and is all that is required for germination. But the plant requires 

 something more ; for if light be excluded, vegetation proceeds 

 imperfectly, and the plant does not then acquire its proper color 

 and other active prope>-*,ies which it ought to have. The chio! 



