OXIDATION IN HEALTHY AND DISEASED APPLE BARK 
DEAN H. ROSE 
During an investigation of oxidase activity in the bark of trees 
affected with Illinois canker, caused by Nummularia discreta (Schw.) 
Tul., there appeared an interesting correlation between oxidation, 
as measured by BUNZEL’s simplified apparatus (1), and the acidity 
of the bark extracts. These were made, in a manner to be described 
later, from material of three different kinds: (1) green bark from 
limbs of trees unaffected by canker; (2) green and still seemingly 
healthy bark from trees badly affected by canker; (3) brown dis- 
eased bark from around the edges of cankered areas. 
Bark obtained during the winter months did not separate easily 
from the wood, but care was taken to make the removal as com- 
plete as possible without scraping or cutting off any of the wood. 
While the diseased bark may have contained fungus parasites other 
than Nummularia, the precautions taken make this unlikely. All of 
the really dead dry bark on the surface of the canker was cut and 
scraped away, until the moist brown or blackened bark around the 
edge was reached. A strip of this 3-4 cm. wide, including some- 
times a little of the green bark next to it, was then cut off down to 
the wood and used as “diseased bark.” The various samples 
obtained were dried to constant weight at 65-70° C., ground up 
almost to a dust with a meat-grinder, and stored in glass-stoppered 
museum jars or tightly corked flasks. The writer realizes, of 
course, the need of tests on extracts from undried bark, and expects 
to carry through a series of them as soon as time and other work 
will permit. 
Extracts for the various experiments were prepared under con- 
ditions which made them quantitatively comparable. In all cases 
distilled water was added at the rate of 8.5 cc. per gram of dried 
ground bark, and toluene at the rate of 0.5 cc. per 100 cc. of water 
used. The beaker containing the mixture was set on top of an 
incubator at a temperature of about 29°C. for one hour, during 
which time the mixture was thoroughly stirred five or six times. 
5s] [Botanical Gazette, vol. 60 
