12 



VEGETABLE PHYSIOLOGY 



the latter undergoing much subsequent differentiation 

 according to their ultimate dimensions and the nature of 

 their habitat or environment. 



The protoplasm being the living substance of the plant 

 is possessed of certain properties which are not shared bv 



FIG. 13. FILAMENTS OF Nostoc. 

 (After Luerssen.) 



FIG. 14. Pediastrum, CONSIST- 

 ING OF A PLATE OF CELLS. 



the framework on which it rests. It is, indeed, the centre 

 of all the activities which the plant manifests. It assimi- 

 lates the food which the plant requires and carries out all 

 the chemical processes necessary for life. It constructs 



FIG. 15. VEGETABLE CELLS. 



A, very young ; B, a little older, showing commencing formation of vacuole. 

 p, protoplasm ; n, nucleus ; v, a vacuole. 



the framework of the plant by which it is itself supported. 

 It receives impressions from without and regulates the 

 responses which the plant as a whole makes to those 

 impressions, both by internal and external movements or 

 changes of position. It is only by its powers of responding 

 to such impressions that the whole organism is able to place 



