103 HOW CKOPS GROW. 



ceeds best in presence of a free alkali, the conditions 

 under which the proteoses of digestion are formed are in 

 part identical with those that give rise to the acid-pro- 

 teids and alkali-proteids. 



Peptones hare been found in small proportions in the 

 water-extract of various plants, e. g., seedlings, lupins, 

 barley-malt, young grass, alfalfa, etc. {Vs. St., XXIV, 

 363, 371, 440, and XXXII, 389.) 



Vines has found a proteose in considerable quantity in 

 the seeds of lupin, peony, and wheat and in the Brazil- 

 nut and castor-bean, and considers bodies of this class to 

 be of general occurrence in the protein-granules of plants. 



The proteose (hemialbumose*) from lupins has, exclu- 

 sive of 0.81 p. c. of ash, the following composition per 

 cent according to Vines : 



Sidney Martiii reports the existence of a proteose 

 (hemialbumose) in the juice of the papaw or melon 

 tree {Garica papaya) where it is associated with the fer- 

 ment papain, which is very similar to that of the pan- 

 creatic secretion of animals. 



Ferments are substances which produce or excite 



chemical changes in a manner as yet mostly unexplained, 



. the ferments themselves not appreciably contributing of 



their own substance to the products of the processes 



which they set in operation. 



The ferments that figure in agricultural chemistry are 

 closely related to and apparently derived from the albu- 

 minoids, but in no case has their chemical composition 

 been positively established. They are distinguished and 

 characterized almost solely by the sources whence they 

 are derived, and the effects which they produce. The 



* Kiihne first distinguished the products of pepsin or trypsin diges- 

 tion into liemlalbumose and antlalbumose, tlie former being converted 

 by trypsin into amido-acids (see p. 114), the latter remaining unaltered 

 by the digestive ferments. Kuhne & Chittendon have more recently 

 shown *' hemialbumose " to be a mixture mainly of proto and dentero- 

 albumose. 



