264 FIRESIDE SCIENCE. 



shadows it with its branches. The plant that 

 adheres to the rock consists of a single cell, but 

 that cell is as perfect and beautiful as any of those 

 which make up the structure of the oak. The tree 

 is but an aggregation of cells ; cells piled upon 

 cells, and the work that is carried on within them 

 is no more complex than that which goes on in the 

 workshop of the humble unicellular plant. , 



It is with a choice of terms that we designate the 

 cell as the workshop of the plant, in which the 

 materials that enter into its organization are elab- 

 orated and fitted to aid in the increase of its 

 substance. The nature of the food which is ma- 

 nipulated within the cell is indeed peculiar, inas- 

 much as plants gather together the waste products 

 of men and animals, and again fit them for the use 

 of higher organisms. Plant food is oxidized food 

 food which it is impossible for animals to assimilate ; 

 and the plant, in all its functions and in the objects 

 of its growth, manifestly occupies an intermediate 

 position between ourselves and the insensible rocks. 

 This is absolutely essential to the existence of man 

 upon the earth. Of all the functions of plants, the 

 most remarkable are connected with, or related to 

 the solar rays, for they possess the power of utiliz- 

 ing the sun's heat in a way which enables them to 

 pull apart, as it were, some of the most complex 

 and refractory compounds known to modern chem- 



