150 THE ELEMENTS OF VEGETABLE HISTOLOGY 



tinguished from starch by their solubility in mineral 

 acids with liberation of carbon dioxide. 



Aleurone. Aleurone granules occur in several 

 different forms and may closely resemble small starch 

 grains. A form frequently seen consists of globular 

 bodies, each containing one or more crystalline struc- 

 tures, or having the latter attached to the outer edge 

 of the grain. Other forms show globular bodies 

 within the grain or attached to its outer edge. The 

 iodine reaction may be used to distinguish between 

 starch and aleurone grains, as the latter become 

 brown upon addition of the reagent. Various types 

 of aleurone grains are illustrated in Plate 52, Nos. 

 4 and 5. 



