420 PROTEINS 



may readily be stained in fuchsin. To do this, the sections 

 should be placed in a 0-2 per cent aqueous solution of acid 

 fuchsin for twenty-four hours, washed in running water and 

 mounted in Canada balsam in the usual way. 



Several proteins may occur in aleurone grains and may be 

 recognized by their different solubilities in water, salt solution, 

 alkali, and alcohol. Also, the details of the composition of 

 these grains are not the same for all plants in which they 

 occur ; for instance, in the paeony the matrix is soluble in 

 water, whereas in the castor-oil plant it is insoluble in water 

 but soluble in a strong aqueous solution of sodium phosphate. 

 According to Bokorny,* globulins are the common pro- 

 teins occurring in the aleurone grains and crystalloids of 

 seeds. It should be remarked that the term aleurone grain 

 is frequently used in a generic sense to include all non-crystal- 

 line reserve protein bodies of a more or less definite shape ; 

 they are not always of the complicated nature described above, 

 thus in the grain of wheat they are quite simple in structure 

 and do not contain a crystalloid nor a globoid. f 



The seed proteins which are soluble in salt solutions are 

 deposited from their solutions when the concentration of the 

 salt is reduced by dialysis, by dilution, or by other means. 

 According to Osborne, $ the deposition of proteins in a crystal- 

 line form within the aleurone grain may be attributed to a 

 similar diminution in the salt content of the cell sap resulting 

 from the formation of the globoid, the calcium magnesium 

 salt of inosite phosphoric acid known as phytin. 



In contrast to the proteins of the seed, which are reserve 

 proteins, those of the leaf are of a more labile nature and may 

 be expected to differ from the former in composition. The 

 method initiated by Osborne and Wakeman § for the investi- 

 gation of the leaf proteins of spinach, consisted in grinding the 

 leaves with water, centrifuging, and coagulating the proteins 

 contained in the resulting colloidal solution by warming to 



* Bokoray : " Bot. Centrbl.," 1900, 82, 289. 



t For an account of the artificial production of protein grains, see 

 Thompson : " Bot. Gaz.," 1912, 54, 336. 



{ Osborne : " The Vegetable Proteins," London, 1924. 

 § Osborne and Wakeman : " J. Biol. Chem.," 1920, 42, i. 



