PROTEINS IN DIFFERENT PARTS OF PLANTS 1 1 



protein in a finely granular condition and without definite form yield 

 relatively small quantities of globulin, for the great mass of the reserve 

 protein isolated from these seeds is insoluble in saline solutions. 

 The proteins isolated from many seeds are apparently obtained with 

 unchanged properties. The crystalline and spheroidal forms exhibited 

 by the proteins within the cells of those seeds which yield large quan- 

 tities of globulin suggest that this protein was deposited within the 

 cell by a process similar to dialysis, by which such forms can be arti- 

 ficially reproduced. 



In those cells of the endosperm in which protein is most frequently 

 found in the form of crystals or of small spheres there is usually ob- 

 served a globule, composed largely of insoluble mineral substance, 

 commonly called a globoid. This globoid was formed from soluble 

 mineral salts contained in the fluid of the cell, and it is possible that, 

 as its constituents passed out of solution, through the formation of an 

 insoluble combination, the concentration of the salts in the cell fluid 

 was correspondingly reduced and the globulin thereby precipitated, in 

 much the same way as occurs when salts are removed by dialysis. 



As already stated, the proteins extracted from seeds are obtained 

 in various forms which represent distinctly different protein substances. 

 The solubility of the protein matter in different seeds varies greatly, 

 but in general it is found that a part is soluble in water, a part is 

 soluble in neutral saline solutions and a part is insoluble in either of 

 these solutions but soluble in dilute solutions of acids or alkalies, while 

 in the seeds of the cereals a part is also soluble in alcohol of from 70 

 to 90 per cent. The proteins extracted from seeds by these several 

 solvents will be considered in greater detail later. 



The possibility of making preparations of proteins which may fairly 

 be considered as chemical individuals deserves special attention. These 

 substances present unusual difficulties in this respect, for they have none 

 of those physical and chemical characters which the chemist usually 

 depends upon to show the individuality of an organic chemical com- 

 pound ; in other words, the proteins have no single property by 

 means of which any judgment can be formed in regard to the strict 

 chemical individuality of any one of them. The best that can be done 

 at present is to establish a constancy of the ultimate composition of 

 successive fractional precipitations of the protein under consideration, 

 and to show the constancy of the physical properties and products of 

 hydrolysis of these fractions so far as this is possible. There can be no 

 question, where differences are found in composition or properties be- 

 tween successive fractions of a protein preparation, that the substance 



