684 SCIENCE PROGRESS 



take place by means of an enzymatic action, and the ammonia 

 is directly used up for the formation of protein. The fusel-oil 

 formation depends not only on the amount of amino acids, but 

 also on the kind and quantity of other nitrogenous substances 

 present. In the presence of easily assimilated nitrogen, such as 

 asparagine or ammonium salts, practically no fusel oil is formed. 

 Ehrlich has also applied this process for the preparation of 

 optically active amino acids from the racemic inactive com- 

 pounds, one component only being transformed into the 

 corresponding alcohol. But not only is yeast able to use 

 leucine and iso-leucine as a source of nitrogen for its protein 

 formation, but also all the other a-amino acids, e.g. tyrosine is 

 converted into p-oxy-phenyl-ethyl alcohol, and phenyl-alanine 

 furnishes phenyl-ethyl alcohol. The formation of this latter 

 substance, which represents the largest bulk of the essential 

 oil of roses, opens a new outlook for another branch of plant 

 physiology, the formation of essential oils and their connection 

 with proteins. 



Carnivorous Plants. — Of great interest is the existence of 

 plants which secrete products analogous to the digestive juices 

 of animals, and which are able to digest insects or proteins. 

 This great group of carnivorous plants comprises Drosera, 

 Pingiiicula, and Utricula varieties, etc. The various kinds of 

 Nepenthes act on a larger scale, catching and digesting insects 

 by means of the liquid in their pitchers. It is still doubtful 

 whether the action of these enzymes corresponds to that of 

 pepsin or trypsin, although some recent preliminary experi- 

 ments by Abderhalden and Terunchi make it probable that 

 it is not of a trypsin nature. They found that the dipeptide 

 glycyl-1-tyrosine is a very convenient substance to distinguish 

 between pepsin and trypsin, as it is not attacked by the 

 former, but easily split into its components by the latter. 

 The juice of Nepenthes has no appreciable action on this 

 dipeptide. Recently Vines has succeeded in showing that an 

 enzyme of the nature of erepsin occurs largely in plants and 

 also to some extent in Nepenthes pitchers. This enzyme was 

 originally discovered by Cohnheim in the intestinal mucous 

 membrane, and it was shown by Vernon to be generally present 

 in all animal tissues. It has no action on proteins as such, but 

 splits peptones, albumoses, and polypeptides into amino acids. 

 One would expect that the carnivorous plants would be able to 



