CLASSIFICATION OF VEGETABLE PROTEINS 81 



named zein by Gorham (135) and maize fibrin by Ritthausen. Zein 

 has been the subject of special study by Chittenden and Osborne (72), 

 by Osborne (308), and by Osborne and Clapp (346). Hordein, which 

 is the prolamin of barley, resembles gliadin in solubility [Osborne 

 (305)] but differs distinctly in the proportion of the amino-acids which 

 it yields on hydrolysis [Osborne and Clapp (342)]. 

 The principal prolamins are therefore : 



Gliadin found in the seeds of j hea '' Tnticum vulgar, (366). 



\Rye, Secale cereale (304). 



Hordein found in the seeds of Barley, Hordeum vulgare (305). 

 Zein Maize, Zea mays (72, 308). 



(e) Albuminoids. 



No representatives have yet been found in plants of the remaining 

 groups of simple proteins, namely, the albuminoids, histones and pro- 

 tamins. That many of the reserve proteins of seeds show relations to 

 the albuminoids has been already pointed out, but the differences in 

 their behaviour toward solvents is so great that none of them can pro- 

 perly be considered to belong to this group. 



(/) Histones. 



The large amount of basic amino-acids which many of the seed 

 proteins yield is similar to that which is considered to be characteristic 

 of the histones, and the reactions of edestan (cf. p. 41) are similar to 

 the reactions of the histones. Whether any real relation exists between 

 histones and seed proteins high in base, or whether the similarity al- 

 luded to is merely accidental, must be the subject of further study. It 

 is possible that the proteins commonly included among histones do 

 not, in fact, differ so widely from other simple proteins as has been 

 generally supposed. 



(g) Protamines. 



No substances in any way similar to the protamines have ever been 

 found in plants, and there is no reason to expect to find them among 

 the reserve proteins of seeds. It is possible that such substances occur 

 in pollen grains, but neither the early investigations by Fourcroy (123), 

 John (180) and Braconnot (55), nor the later ones by v. Planta (379#) 

 of hazel pollen, and by Kammann (183) of rye pollen, have given 

 evidence of their presence. These investigators, however, made no 

 attempts to discover protamine in pollen and its presence is by no 

 means excluded by their work. 



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