156 



Elementary Biology. 



most watery part of the granule. Starch has the same, com- 

 position as cellulose (C 6 H IO O 5 ), but a different constitution. 

 The granule is believed to consist of a skeleton of cellulose, 



FIG. 73 A. -STARCH GRAINS UNDER THE POLARISCOPE. (Vines and Dippel.) 



ha. (Thome.) 



the interstices of which contain the starch proper, or granu- 

 lose. The physiological importance of starch, and of the 

 other differentiation products of protoplasm about to be 

 mentioned, will be referred to in the 

 - next chapter, where a general sketch 

 w m j^ gj ven o f t ^ e more important 

 phenomena in the physiology of plants. 

 Inulin, a chemical ally of starch, is 

 found abundantly in the roots of many 

 plants (e.g. the daisy tribe). It however 

 differs from starch in that it exists in 

 solution in the cell-sap, from which it 

 may be precipitated by the action of 

 alcohol, in the form of crystalline 

 spheres, usually adhering to the cell- 

 wall (fig. 74). 



Aleurone is to be considered as a 

 proteid reserve material (fig. 75). It is usually found in the 

 form of grains which lie embedded in an oily matrix. It 



