J. C. Draper—Evolution of Structure in Seedlings, 897 
Table [V.—Seedlings grown in the light. 
Night growth. Day growth. 
No. 5 34 inches. 4 inches, 
No. 6 Bogs a 
No. re 5 4 “ 4 4 74 
No. 8 a a 
Average, 64 “ Average, 6 “ 
Having established the continuous character of growth in 
seedlings, and the similarity of rate and nature of the process 
by night and by day, and admitting that at night plants throw 
olf carbonic acid, it is not improbable that this carbonic acid 
arises, not from mechanical absorption by the roots, and vapori- 
zation by the leaves, but as a en result or concomitant of 
the act or process of evolution of structure, 
To put the matter in the clearest form, let us first under- 
Stand what growth is. It appears in all cases to consist in the 
evolution or production of cells from those already existing. 
According as the cireumstances under which the cells are pro- 
now we examine the evolution of cells under the simplest 
conditions, as for example in the fermentation that attends the 
manufacture of alcohol, we find that with the evolution of the 
torule cells carbonic acid is produced. The two results are 
intimately connected, and it is proper to suppose that since the 
carbonic acid has arisen along with the new cells, the latter 
Operation must in some way involve a process of oxidation. 
Accepting the hypothesis that oxidation is attendant on these 
processes of cell growth under the simplest conditions, we pass 
