224 PRACTICAL BOTANY 



cut thin sections from it, and mount in the oil. Examine 

 under a high power, and observe 



1. The thin cell-walls of the oval cells. 



2. The numerous highly refractive aleurone-grains 

 in each cell ; each is of oval form, and a less highly 

 refractive area is seen at one end: this is the 

 globoid. 



3. The oily matrix in which the grains are em- 

 bedded, this being so transparent as to be hardly 

 visible. 



Cut other sections with the razor wetted with alcohol, 

 soak them well in alcohol in a watch-glass to dissolve 

 the oil out of them (ether is a more ready solvent of 

 the oil, and may be used instead of alcohol : wash off 

 the ether with alcohol), and mount in pure glycerine : 

 examine them under a high power, and observe the 

 appearance of the aleurone-grains as before when seen 

 in oil. 



i. Add water gradually, and watch its effect on the 

 grains. 



1. The outer amorphous coat of the grain will 



swell, and become less highly refractive : thus 

 there will be disclosed 



2. The crystalloids, one (or rarely more) being 



included in each grain : these do not swell 

 greatly with water, and accordingly they 

 retain their refractive power. 



3. The globoid will also be visible as before. 



ii. Add dilute potash solution : the amorphous coats 

 and the crystalloids will swell and dissolve, leaving the 



globoids. 



iii. Add strong acetic acid : the globoids will dissolve 



