. Botanical gazette. Plants. iQig] ROSE—BLISTER CANKER 109 although the ratio between the two is greater where benzidine or guaiacol was used as oxidase reagent than where pyrogallol was used. The writer prefers to follow Bunzell in using the term oxidase activity or oxidizing power rather than ''; Where the latter term occurs in this paper, it is used only for the sake of brevity, with no intent to imply any fixed notion as to the nature of the agent which brings about the oxidation. Titration and indicator tests on extracts of fresh bark showed the healthy bark to be more acid t
. Botanical gazette. Plants. iQig] ROSE—BLISTER CANKER 109 although the ratio between the two is greater where benzidine or guaiacol was used as oxidase reagent than where pyrogallol was used. The writer prefers to follow Bunzell in using the term oxidase activity or oxidizing power rather than ''; Where the latter term occurs in this paper, it is used only for the sake of brevity, with no intent to imply any fixed notion as to the nature of the agent which brings about the oxidation. Titration and indicator tests on extracts of fresh bark showed the healthy bark to be more acid than the diseased, exactly as had been shown previously in the work with dried bark. No data J) D-- - ../J-- ^_ -'C^. Fig. I.—Oxidation of pyrogallol, guaiacol, and benzidine by extract of fresh bark, healthy and diseased, and extract of dried bark, healthy and diseased: A, pyrogallol and fresh health)^ bark; B, pyrogallol and fresh diseased bark; C, ben- zidine and fresh healthy bark; D, benzidine and fresh diseased bark; E, guaiacol and fresh healthy bark; F, guaiacol and fresh diseased bark; G, pyrogallol and dried healthy bark; H, pyrogallol and dried diseased bark; // = healthy, Z) = diseased. are given, since the true condition, at least for dried bark, was determined more accurately by means of a potentiometer. Extracts of dried bark.—For the work at the University of Chicago bark was used which had been dried at 35-40° C. for 2-3 hours, ground fine enough to go through a 40-mesh sieve, and stored air dry in zinc-capped Mason jars. A few of the experiments were run with oxidases precipitated from an extract of this bark powder, but in most of them the powder itself was used, gm. in each apparatus. The reagents tested were pyrogallol and pyro- catechin, 4 cc. of a i per cent solution; benzidine gm.;. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of thes
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