CELL-CONTENTS AND CELL-WALLS. 45 



Note the numerous small refractive protein grains, 

 which at first sight may resemble starch grains, but are 

 not stratified and turn brown, not blue, with iodine. Of 

 these simple grains, some are soluble in water (Almond, 

 Apple) ; others, insoluble in water, are soluble in saturated 

 salt solution either at once (Beans, Peas, Lupin), or after 

 treatment with alcohol (Sunflower). 



In each case treat different sections with (1) water 

 even when this does not dissolve the grains, it usually 

 makes them swell and lose their bright appearance ; 



(2) potash this makes the grains swell and dissolve ; 



(3) iodine this turns the grains brown ; (4) Biuret test ; 

 (5) Xanthoproteic test ; (6) Millon's reagent. 



52. Protein Grains with Crystalloids and Globoids. 



Brazil nut and Castor Oil seeds form good material 

 for the study of the larger and more complex protein 

 or " aleuroue " grains, which are embedded in the oil- 

 containing protoplasmic matrix of the cells. These grains 

 are not soluble in water, but are dissolved by strong salt 

 solution, either at once (Brazil nut) or after treatment 

 with alcohol (Castor Oil, Walnut). In each case remove 

 the shell, and make the following preparations. In each 

 case cut the sections with the razor dry, except where 

 otherwise directed. 



(a) Mount dry sections in thick glycerine the oily 

 matrix of the cells will be seen, with the oil drops ; note 

 the protein grains, in which the crystalloids and globoids 

 may be seen. 



(b) Mount sections in olive oil (which may in this case 

 be used for wetting the razor). Note that the oil makes the 

 oily matrix of the cells transparent and almost invisible. 



(c) Wet the razor with alcohol, cut sections, soak them 

 in alcohol to dissolve out the oil (ether will do this more 

 quickly wash out the ether with alcohol), and mount in 

 thick glycerine. 



(d) Cut dry sections, and mount them in water this 

 makes the grains swell, but the crystalloids should become 

 more conspicuous. Irrigate sections, mounted in water, 



