394 The Physiology of Plants BOOK in 



of alkalies, and alcohol. He classified the proteins he pre- 

 pared into three groups as follows : 



1. Albumins : soluble in water ; solution coagulating 

 on boiling. 



2. Caseins : slightly soluble in water, readily soluble in 

 dilute solutions of potash or of basic potassium phosphate : 

 precipitable from such solutions by addition of dilute acids. 



3. Gelatines ; soluble in alcohol and in dilute acids. 



He described several members of his second and third 

 groups, which differed from each other by exhibiting vary- 

 ing degrees of solubility and by yielding different products 

 of decomposition. 



Weyl, who took the matter up in 1877, returned to the 

 methods of the animal physiologists, holding that the sol- 

 vents used by Ritthausen led him to overlook the existence 

 of globulins and in many cases altered the composition of 

 the proteins during the process of extraction. He re- 

 affirmed the occurrence of globulins in seeds and identified 

 members of the groups of myosins and vitellins, which were 

 recognized at that time by the animal physiologists. The 

 gluten of flour, which Ritthausen had classed among his 

 gelatines, Weyl held to be derived from globulins, possibly 

 by a species of coagulation akin to the coagulation of blood. 



Into the controversy which followed, considerations of 

 space will not allow us to enter. Ritthausen replied at 

 once to the contentions of Weyl and Hoppe Seyler, main- 

 taining his position with some energy in 1877 and again 

 in 1879. Weyl was supported by Schmiedeberg in 1877 

 and by Griibler in 1881. 



Many observations on the grains of various seeds were 

 made at about the same time as to the solubility of the 

 aleurone in different reagents, especially by Pfeffer in 1872 

 and Tangl in 1877, but they threw little light upon the 

 problem. 



The observations of Vines, published in 1878-80, consider- 



