CHAPTER IV 



ABSORPTION AND MOVEMENT OF WATER FOOD DISTRIBUTION 



In the preceding chapter we have discussed the elements 

 and their compounds, which constitute the food-materials of 

 plants, and we have gained some idea as to when, by what 

 means, and through what stages these are elaborated into 

 foods. How foods are assimilated — rendered like the living 

 protoplasm which they are to nourish — is not now evident. 

 We have finally seen that these assimilated foods may be 

 incorporated into and made a part of the living protoplasm, 

 but how this is accomplished remains one of the wholly 

 unsolved problems of physiology. 



We must now consider how the plant absorbs its food- 

 materials and transfers from part to part the foods which 

 it elaborates from them. These processes underlie and at 

 the same time form an essential part of nutrition, but 

 since other substances than those needed and used as food- 

 materials and foods are concerned, we may well consider 

 this subject by itself. 



With the exception of water, which is both a food-material 

 and the vehicle of nutrient substances, the food-materials of 

 animals and plants are of two sorts — either gases or solids. 

 The latter are available only in solution, entering the body 

 and passing from part to part only when dissolved in 

 water. * The absorption and transfer from part to part in 

 the plant-body of the gaseous food-materials — carbon-diox- 



* The apparent contradiction to this statement offered by the Myxoniy- 

 cetes, Amoebn. etc. — naked masses of protoplasm not enclosed by cell-wall — 

 which may in their movements surround solid particles, both innutritious 

 and nutritious, is not a real one. Only those particles which are soluble 

 and dissolved are absorbed by the protoplasm and really enter it; the 

 others are left unaffected by it although they may remain enclosed for a 

 time. 



