THE ENERGY OF THE LIVING PROTOPLASM. 
179 
of Dauern , Beta , Lactuca , and Taraxacum. Among the algæ 
Zygnema 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. 
Sclwnbein observed this blue reaction in various seeds, and 
especially well in those of Cunara ; (2) 3 Molisch in the secretions of 
various roots, as those of Pisum, Brassica , Cucurbita, Lepidium, 
Scorzonera and Neottia. {3) 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 Zygnema 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; Gmelin-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. Schöne (Z. analyt. Chem., 33, 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, C20 H24 O5 (Lücker). 
