126 



BOTANICAL GAZETTE 



[FEBRUARY 



(fig. 5). Table XVII, however, shows that gelatine has little 

 effect on the hydrogen ion concentration of oxidizing mixtures of 

 either healthy or diseased bark. 



Precipitated oxidases. — Experiments were run using pre- 

 cipitated "oxidases," prepared as follows: 2 gm. of bark were 

 allowed to extract with 10 cc. of water and 5 drops of toluol for 

 I hour; the extract was then squeezed through moist cheesecloth 

 on to coarse filter paper, the beaker washed with five i cc. portions 

 of water and the filter paper finally with two more; 50 cc. of 95 per 



1 2 3 



20 



44 



Fig. 5. — Effect of 0.8 per cent gum arable and 0.8 per cent gelatine on oxidation 

 of pyrogallol by healthy and diseased bark: A, healthy bark; B, healthy bark and 

 gum arable; C, healthy bark and gelatine; D, diseased bark; E, diseased bark and 

 gum arable; F, diseased bark and gelatine. 



cent alcohol were then added to the filtrate (concentration of alcohol 

 about 70 per cent), the whole allowed to stand for 10 minutes and 

 the flocculent precipitate collected on a hard filter by gentle suction 

 with a filter pump; 150 cc. more alcohol were then added to the 

 filtrate (concentration of alcohol now about 90 per cent) and the 

 whole allowed to stand for i hour, since precipitation was slow, 

 before collecting this second fraction on the filter with the first. 

 The precipitate from diseased bark was much browner than that 

 from healthy bark. Whether this bears any relation to its greater 

 oxidase activity is not known. 



