106 



carbonate solution, which caused the purple oxidation product 

 to dissolve. 



Phenol was used in a 5 per cent, aqueous solution and became 

 reddish brown in twenty-four hours if oxidized. 

 . The phenolphthalin and indo-phenol reagents oxidize spon- 

 taneously in the air and must be freshly prepared for satisfactory 

 use. 



In testing for the chromogens in the various plants we merely 

 allowed some of the juice to stand for twenty-four hours, when the 

 chromogens became evident by being changed by the oxidases 

 to the colored state, generally brown, reddish or black. 



For the detection of oxidases in plant sections, under the micro- 

 scope, one may use the a-naphthol reagent described above, either 

 with or without hydrogen peroxide. Under these conditions 

 oxidizing tissues or cells soon stain violet or lavender and make 

 a beautiful picture until the diffusion of the oxidases is complete 

 and the whole preparation becomes dark. Sections of vines 

 containing much food-conducting tissue, such as Aristolochia 

 macrophylla, stain very strikingly as a result of this treatment. 





Summary of 



Oxidase Tests 







Specimens Examined 



Oxygenase 



Peroxidase 



Catalase 



Chromogens 



All parts (no) 



55 



78 



105 



30 



Leaves (17) 



12 



12 



16 



6 



Floral organs (20) 



8 



II ■ 



20 



7 



Tubers, bulbs, etc. (21) 



14 



20 



19 



7 



Fruit (41) 



13 



28 



40 



7 



Other parts (11) 



8 



7 



10 



3 



Study of the Effect of Acidity upon Oxidases 

 In the course of our systematic search for the oxidases, it soon 

 became evident that an acidity in the plant juices and extracts 

 greater, per lo c.c. of plant liquid, than the alkalinity of 0.8 c.c. of 

 N/io KOH solution, with phenolphthalein as the indicator, usu- 

 ally indicated the absence of oxidases in the plant part under 

 examination. These observations led the writer to study this phe- 

 nomenon further. It was found that 10 c.c. of lemon juice re- 

 quired 18.5 c.c. of N/io KOH solution for neutralization, and did 

 not show the presence of oxidases either before or after neutraliza- 



