144 BOTANICAL GAZETTE [avcusT. 
produce certain striking postmortem changes in animal and pla 
tissues. I refer in particular to the postmortem discolorations ¢ 
certain organic compounds which are produced by the oxidizi 
activity of these enzymes. The most striking illustration of th 
oxidation and discoloration in plants was pointed out, in 1883, by 
Japanese, H1koROKURO YASHIDA, who discovered that the forma 
of black varnish by the oxidation of the latex of the lac tree wé 
produced by the intervention of an oxidizing ferment. Since th 
discovery, the activity of oxidizing enzymes has been carefully studied 
in the discolorations which are produced by them in the extra 
juices of fruits, vegetables, cereals, mushrooms, and other soft p 
tissues. These investigations have shown conclusively that, as 
the case of the oxidation of the latex of the lac tree, postmort 
discolorations are produced in these juices by the intervention 
oxidizing ferments. This change of color which is produced in # 
tests for oxidizing ferments. A strong blue color produced in 
alcoholic tincture of guaiacum, in the presence of oxygen or hydro 
peroxid, indicates the presence of oxidizing enzymes. Upon the 
of these tests certain authorities divide oxidizing ferments 
oxidases and peroxidases, according to whether the blue com 
produced in the tincture of guaiacum occurs in the presence of oxy 
or hydrogen peroxid. 
It is of interest to note the behavior of oxidizing ferments une a 
variations of temperature. Investigation has shown that optimu 
temperatures exist for oxidizing enzymes at which they react W! 
great activity. Below these optimum temperatures their activ! 
decreases, and similarly in increasing thé temperature above 
optimum their activity decreases, and in almost every case ? 
activity is entirely destroyed before a temperature of 100 C. is atta 
The activity of oxidizing ferments is also decreased or destroy’ 
by certain antiseptics, and by other chemical substances. 
From this consideration of certain properties of oxidizing e? 
we see that there exists a strong similarity between theit oxidi 
activity and the chemical reactions which produce sap stain- 
each <—- pao oxidization with change of color is P 
by t with the air (oxygen), and variations in ter 
