224 NUTRITION EFFECTED BY CELLS. 



that carbon is fixed from the air ; these same cells are the in- 

 struments of the functions of exhalation and respiration, and of the 

 final elaboration of the sap ; other cells, dispersed through various 

 parts of the plant, have the office of secreting or separating from 

 this some of its peculiar contents ; and lastly, it is by the action 

 of cells (as we shall hereafter see, Chap, xn.), that the process of 

 reproduction is carried on, in the highest, as in the lowest. Thus 

 in regard to the actions of the cells, of which they are respectively 

 composed, there is but little difference between the simplest and 

 most complicated Vegetable structures ; the distinction being 

 chiefly in this, that among the former, one cell may discharge 

 all these offices ; whilst in the latter, the several functions are 

 performed by distinct cells, adapted to them alone. 



