18 



centage of albuminous compounds for air-dried crops are given as 

 follows : 



This crude chemical analysis of the walls and of the contents of the 

 crushed cells tells us nothing of the life that had previously resided 

 in the uncrushed organisms, but prepares us for the statement that 

 the development of a plant implies a great amount of work done 

 among the molecules in rearranging them into the places where 

 tliey are needed. These molecules come from the simpler atoms in 

 the soil, the air, and the rain water, but the force and energy that 

 does the work of building them up comes, so far as we know, from the 

 sunshine. It is a case of the transformation of energy. Within the 

 cells of a plant the molecular energy, or the so-called " radiant 

 energy," that would otherwise produce the phenomena of heat and 

 light is transformed into chemical activity and produces the new 

 molecular compounds that we use as food. We and other animals 

 can not produce these compounds in our own bodies, but we can utilize 

 them if they are not injured in the process of cooking. 



GENERAL RELATIONS OF THE SEED AND PLANT TO THE AIR 

 AND THE SOIL. 



RESPIRATION. 



It is known that in the act of germination the seed absorbs oxygen 

 from the air contained in the interstices of the soil and that very few 

 seeds will germinate when the soil and the water are deprived of air 

 or free oxygen. 



As to the full-grown plant, it is commonly said to absorb carbonic- 

 acid gas from the air through its leaves and to exhale oxygen. The 

 investigations of Moisson tend to modify this statement and show 

 that at low temperatures there is more oxygen absorbed than there 

 is carbonic-acid gas produced, while at high temperatures the reverse 

 is true. For each plant there is a certain temperature at which each 

 volume of carbonic-acid gas absorbed is replaced by an equal volume 

 of oxygen exhaled by the leaves. Thus in the case of the Pinus 

 pinaMer for every 100 volumes of oxygen absorbed there are 50 

 volumes of carbonic-acid gas exhaled at 0° C. temperature, but 77 

 volumes at 13° C. and 114 volumes at 40° C. 



