THE ENERGY OF THE LIVING PROTOPLASM. 



179 



of Daucus, Beta, Lactuca, and Taraxacum. Among the algae 

 Zygncma may be mentioned, whose fresh juice turns black, and 

 among the fungi Boletus luridus, whose freshly cut surface turns 

 blue in contact with air. (I) If, however, oxidising enzymes 

 are present while those oxidisable compounds are wanting, then 

 the existence of the former can be shown by adding guaiacum 

 solution or hydroquinone, pyrocatechin, or pyrogallol. Guaiacum 

 will yield a blue color, the latter a brown or black one. 

 Schunbcin observed this blue reaction in various seeds, and 

 especially well in those of Cunara Molisch in the secretions of 

 various roots, as those of Pisum, Brassica, Cucurbita, Lcpidiuni, 

 Scorzonera and NeottiaP ] Some observations of Pfeffer have 

 made it probable that the supposed enzymes are contained in 

 the protoplasm itself, and come therefore into intimate contact 

 with the easily oxidisable compounds contained in the cell-sap only 

 after the death of the cells, when the osmotic properties of the 

 tonoplast have gone.' 4 ' That the blue colouration of guaiacum is 

 also due to the action of an enzyme is supported by the fact that 

 fresh diastase can produce the same reaction. (5) I have further 

 observed that an enzyme-like compound of proteid nature can be 

 precipitated from potato juice by alcohol, and that it loses its 

 quality of blackening hydroquinone upon drying in the exsiccator. 

 I have also observed that the blackening of Zygncma never 

 takes place after killing the cells with sulphuric acid or absolute 

 alcohol. Toyonaga determined the temperature at which the 

 potato lost its peculiar action upon hydroquinone, pyrogallol, and 

 pyrocatechin, and found it to be 73 0 . Mercuric chloride destroyed 

 its qualities at 55 0 in one hour, formic aldehyde (5 %) after 2 



(1) Also the cambial sap of the conifers turns gradually brown in contact with 

 air. The turning brown of blossoms and green leaves which sets in after death, 

 belongs to the same group of phenomena. The existence in plants of oxidising 

 enzymes was recently also shown by Bertrand C.r. 120. 



(2) Journ. prakt Chem., 88 and 105; Gmclin-Kraut, I. 2. p. 456. 



(3) Wien. Akad. Ber. 1887. 



(4) The compound yielding the colouration of potato juice can be extracted 

 with alcohol ; it turns dark brown in contact with Fe Cl 3 . 



(5) E.Schi'me (Z. analyt. Chem., :{:$, 159) observed that old guaiacum tincture 

 yields a greenish blue colouration with diastase alone ; fresh tincture, however, 

 wants the addition of hydrogen peroxide. The substance yielding the blue product 

 is guaiaconic acid, C 20 H24 0 5 (Likker). 



