Blister canker of apple trees; a physiological and chemical study .. . The results indicate thatfor approximately equal amounts of dry matter the dried bark isconsiderably less active than the fresh (fig. i). The decrease isprobably due to the drying; this is shown more definitely by datato be presented later. It is to be noted that the oxidase activityof diseased bark is definitely greater than that of healthy bark, igig] ROSE—BLISTER CANKER 109 although the ratio between the two is greater where benzidine orguaiacol was used as oxidase reagent than where pyrogallol wasused. The writer prefer
Blister canker of apple trees; a physiological and chemical study .. . The results indicate thatfor approximately equal amounts of dry matter the dried bark isconsiderably less active than the fresh (fig. i). The decrease isprobably due to the drying; this is shown more definitely by datato be presented later. It is to be noted that the oxidase activityof diseased bark is definitely greater than that of healthy bark, igig] ROSE—BLISTER CANKER 109 although the ratio between the two is greater where benzidine orguaiacol was used as oxidase reagent than where pyrogallol wasused. The writer prefers to follow Bunzell in using the termoxidase activity or oxidizing power rather than oxidase. Wherethe latter term occurs in this paper, it is used only for the sake ofbrevity, with no intent to imply any fixed notion as to the nature ofthe agent which brings about the oxidation. Titration and indicator tests on extracts of fresh bark showedthe healthy bark to be more acid than the diseased, exactly ashad been shown previously in the work with dried bark. No data. Fig. I.—Oxidation of pyrogallol, guaiacol, and benzidine by extract of freshbark, healthy and diseased, and extract of dried bark, healthy and diseased: A,pyrogallol and fresh healthy bark; B, pyrogallol and fresh diseased bark; C, ben-zidine and fresh healthy bark; D, benzidine and fresh diseased bark; E, guaiacoland fresh healthy bark; F, guaiacol and fresh diseased bark; G, pyrogallol and driedhealthy bark; H, pyrogallol and dried diseased bark; //? = healthy, Z) = diseased. are given, since the true condition, at least for dried bark, wasdetermined more accurately by means of a potentiometer. Extracts of dried bark.—For the work at the Universityof Chicago bark was used which had been dried at 35-40° C. for2-3 hours, ground fine enough to go through a 40-mesh sieve, andstored air dry in zinc-capped Mason jars. A few of the experimentswere run with oxidases precipitated from an extract of this barkpowder, bu
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