ALEURONE AND CRYSTALLOIDS. 5? 



agents, as organic acids, diastase, and pepsin, also are solvents of 

 granulose. 



(/) The natural solution of starch grains takes place in the cells of 

 living plants in a way somewhat similar to the artificial removal of 

 granulose. The process is not, however, so regular and uniform ; 

 holes and irregular excavations are formed in the grains, sometimes 

 with the removal of the granulose only, and in other cases with the 

 solution of the whole substance ; sooner or later the grains break up 

 into pieces, and by a continuation of the process of solution they soon 

 disappear (Fig. 45, a, g). Sachs maintains that starch may thus be 

 dissolved in the cotyledons of the bean and transferred to other parts 

 of the plantlet, reappearing in the form of grains without undergoing 

 chemical change or conversion into sugar. 



(g) Observations upon the formation and disappearance of starch 

 grains in the chlorophyll-bodies are best made with Spirogyra. By 

 keeping healthy filaments of this plant in darkness for some time the 

 starch disappears ; upon exposure to direct sunlight the formation of 

 starch begins again in about two hours; in diffused daylight it begins 

 several hours later. Other plants with thin tissues may also be used, 

 as, for exainple, the thin leaves of mosses, etc. 



(h) The development and growth of starch grains may be studied in 

 the ripening grains of Indian corn, by making extremely thin sec- 

 tions at different stages of the ripening process. They always appear 

 at first as minute solid globular masses in the protoplasm. 



III. ALEURONE AND CRYSTALLOIDS. 



73. In the ripening of seeds and the maturation of tubers 

 the loss of water by the protoplasm gives rise to a number of 

 poorly understood forms of albuminous matter. Two of the 

 most noteworthy of these are Aleurone, and the crystal-like 

 bodies known as Crystalloids. 



74. Aleurone occurs in the form of small rounded 

 grains, sometimes occupying a great portion of the cavity of 

 the cell (Fig. 44, a, p. 54). They are soluble in water,* or 

 in water containing a little potash ; but are insoluble in alco- 

 hol, ether, benzole, or chloroform. They frequently contain 

 other bodies enclosed in their substance, as crystalloids (de- 

 scribed below), globoids (composed of a double calcium and 

 magnesium phosphate), and crystals of calcium oxalate. 



* The aleurone grains of Cynoglossum, officinale are stated by Sachs 

 not to be soluble in water. 



