374 
Journal of Agricultural Research 
Vol. II, No- s 
that the increased ash is probably responsible for the increased oxidase 
activity, judging from the work of Bertrand (1897) and others (Dony- 
Henault, 1908; Dony-Henault and Van Duuren, 1907; Trillat, 1903 and 
1904). The diminution of the starch and protein in the diseased tubers 
is the net result of the increased combustion of their cleavage products. 
Doby (1911-12) measured the oxidation of pyrogallol according to the 
method of Bach and Chodat (1904), with and without the addition of 
hydrogen peroxid, and also measured the oxidation of tryosin according 
to an optical method (Konig and Kriiss, 1904). In general, the peroxidase, 
oxygenase, and tyrosinase were present in larger quantities in the curly- 
dwarf tubers than in the normal ones. 
With the manometric method devised by the writer, it was found that 
in sugar beets affected with curly-top the oxidase content of the foliage 
is two to three times as great as that of normal beet leaves. This same 
difference was found to exist when plants were studied whose growth 
had been retarded by causes other than the curly-top (1912). 
DESCRIPTION OF EXPERIMENTAL METHODS 
Eor all of the experiments with leaves, fresh material was used—that 
is, plants collected on the day of experimentation. In the case of tubers 
it was sometimes necessary to allow them to lie for a few days until 
enough material for a complete series of experiments had accumulated. 
During the whole period of 10 weeks the plants were collected in the 
field at 7.15 a. m. and taken to the laboratory at once. The weight of 
the foliage was there determined and the material then ground up in a 
meat chopper. The juice was pressed out of the pulp by hand through 
a silk cloth. 
Nearly all of the experiments with normal material were made on 
plants of one variety, the Green Mountain. With one or two intentional 
exceptions the samples of normal plants were taken from the same field. 
They were grown under fairly uniform conditions of environment, and 
the soil was fertilized uniformly with the same fertilizer. All of the 
pathological material was collected on a field several miles away, neces¬ 
sarily from plants of different varieties, but all grown on the same type 
of soil and with the same kind of fertilizer as that used in the field on 
which the normal plants were collected. In most cases 25-gram samples 
of the juice were preserved with about 100 c. c. of 25 per cent alcohol, in 
order that the solid contents of the juices examined might be determined, 
in case it seemed necessary. 
The experiments were carried out in the same manner as that described 
in a former publication (Bunzel, 1912). The following 18 ring com¬ 
pounds were used as reagents to determine the oxidase activity of the 
juices: Benzidin, pyrogallol, alphanaphthol, leuco base of malachite 
green, phloroglucin, aloin, pyrocatechol, tyrosin, hydrochinone,phloridzin, 
