THE NITROGEN COMPOUNDS IN PLANTS 151 



of ammonia in proportion to the amount of glutaminic 

 and aspartic acids, and must, therefore, contain those 

 amino acids in a form different from that of the amide. 

 This protein has also been found to contain very little sulphur. 

 The proteins from leguminous seeds resemble one another 

 in many respects, but differ from those of the cereals. The 

 proteins of the pea, horse bean, lentil, and vetch all yield 

 preparations of legumin which are apparently identical. 

 Other members of the leguminous series yield proteins which 

 are very similar to those yielding legumin, and though not 

 identical, are much nearer to legumin than any of the 

 proteins found in the cereals. The legumin of soy bean is 

 used in Japan to make a vegetable cheese. The soy beans 

 are treated as in the manufacture of starch (see p. 117), 

 but the non-starch residue is kept, boiled, strained, and 

 precipitated with brine. The cheese resembles a half milk 

 cheese. 



The Proteins in Root Crops. Early investigators 

 examined the proteins of the potato, but no great amount 

 of work has been done in this group. The hydrolysis of 

 the protein of the swede turnip produces substances which 

 differ from those yielded by the legumins chiefly in the 

 following points : The percentage <of arginine resembles 

 that yielded by the ceieals, and is distinctly less than that 

 from the leguminous crops. The percentage of histidine 

 is rather high. The percentage of lysine is faitly high, and 

 corresponds to that from the legumes. The low content of 

 glutaminic acid in the soluble protein of swedes will counter- 

 balance the high content of that amino acid in the proteins 

 of cereals when these two are fed together, as is common in 

 ordinary farm practice. Both cystine and tryptophane are 

 also present in the swede protein. 



The Proteins of the Oil Seeds. The globulin in 

 castor bean can be freed by dialysis from all but minute traces 

 of the toxic substances contained in the beans, a fact which 

 forms one of the best pieces of evidence that these materials 

 can be obtained in at least some degree of purity. Edestin, 

 the chief protein of hemp seed, is entirely insoluble in water, 



