CELL-CONTENTS. STARCH. 



423 



forming a similar office in the economy of plants as that of fat in ani- 

 mals. ^ It occurs in all plants at some period of their existence, and is 

 the chief and great mark of distinction between the vegetable and ani- 

 mal kingdoms. Its presence is detected by testing with a solution of 



*BV* f ^0: 



fig. 203. 

 1. Portion of the husk of Wheat, showing siKoeous crystals. 2. SUioeous cuticle of 

 blade of Grass {Pharus cristatus). 3. SUiceous cuticle from under surface of leaf of 

 Deutzia scabia. i. Section of a Cane ; the cell-walls of silica, and internal pores 

 filled with granular matter. 



iodine, which changes it to a characteristic blue or violet colour. Being 

 insoluble in cold water, it can be readily washed away and separated 

 from other matters contained in the cellular parts of full-grown plants. 

 It is often found in small granular masses in the interior of cells. 



