NUTRITION: THE WORK AND THE MATERIALS. 11 



with the water, of the food materials, and their transfor- 

 mations within the plant, is the work of the chemist, and 

 their history must be sought in chemical books. 



Continuous Changes in Plants. In this place we must 

 confine ourselves to the few passing references already made, 

 but one thing we must strive to impress forcibly on the 

 reader, because, if the notion is well grasped, it will enable 

 him to understand plant life so much more vividly. We 

 allude to the continual changes that are going on through- 

 out the whole living fabric of the plant while in its active 

 condition. Cell membrane, the protoplasm, the entire mass 

 of liquid and solid constituents of which the plant consists, 

 are, as we have seen, made up of molecules, each, as it 

 were, with a life of its own, undergoing continual changes 

 according to different circumstances, acting and reacting 

 one upon another so long as any active life remains. Active 

 life, indeed, is ceaseless change ; dormant life is a condition 

 of equilibrium, more often talked about than realised in 

 fact, it is merely relative it implies merely a lessened 

 degree of activity. From this physical point of view the 

 death of a cell is only a change, a rearrangement of particles, 

 never, however, to be recombined into a new growing cell, 

 as happens in the case of a still living cell in the full tide 

 of growth and activity. 



Nutritive Value of the Substances absorbed by Plants. 



The importance of water may be judged from the fact 

 that while succulent vegetables contain more than 90 per 

 cent, of water, timber felled in the driest time seldom 

 contains less than 40 per cent. (Warington). 

 As to the nature of the saline substances, reference 



