396 The Physiology of Plants BOOK in 



but these were almost certainly compounds of the protein 

 with magnesium. 



The proteins named gelatines by Ritthausen we saw were 

 said by him to be soluble in alcohol. The existence of 

 proteins possessed of this peculiarity was first noticed in 

 1820 by Taddei, and in 1821 by Gorham. One of them was 

 investigated more completely by Chittenden and Osborne 

 in 1891 and found to compose a considerable part of the 

 proteins of the maize grain. They gave it the name of 

 zein, which had been first employed by Gorham. It seems 

 to have been described by Ritthausen under the name of 

 gluten-fibrin. Osborne and Voorhees found that the gluten 

 of wheat flour is formed by the interaction of two proteins 

 of this class, which they called gliadin and glutenin respec- 

 tively. These proteins were extracted separately from the 

 flour, but the authors gave no account of their relation to 

 the aleurone grains. It is possible that they exist in 

 amorphous condition in the cells. The name gliadin was 

 used by Taddei, and the protein was described as plant- 

 gelatin by Liebig. The proteins of the wheat grain were 

 investigated by Miss O'Brien in 1895. A similar substance, 

 named hordein, was found by Osborne to be a constituent of 

 barley. The work done in Osborne's laboratory was not 

 complete in 1900 but has been continued to the present 

 time, indeed is still proceeding. 



Reserve proteins have been detected in other places than 

 seeds and in other forms than aleurone grains. Crystal- 

 loids had been observed before 1860 in the ovule of Lathraea, 

 and in the potato tuber ; they were subsequently shown 

 by Vines to consist of vitellin, a form of globulin ; they 

 were seen in the Florideae by Cramer in 1862 and by Klein 

 in 1881, also in certain fungi by the last-named author, and 

 by Van Tieghem six years earlier. In the amorphous form, 

 or perhaps in solution in the cell sap, Zoller found a form 

 of globulin in the potato tuber in 1880, and Zacharias 



