104 
Journal of Agricultural Research 
Vol. XXXI, No. 2 
Minn. The Minnesota test was conducted by J. G. Leach, who 
planted the seed, made the inoculations, and kindly furnished the 
authors with a copy of his notes on disease prevalence. 
The field plots were generally laid off in rows, 3 to 4 feet apart and 
from 100 to 200 feet long, divided into rod units, each unit being 
planted to a single variety which was sometimes replicated in other 
parts of the same plot. As a rule every tenth row was planted with 
infected seed of a very susceptible type, to serve as a control and to 
supply inoculum to the adjacent lots. 
In addition to frequent artificial inoculations, natural infection 
and spread of the diseases were facilitated by scattering between the 
rows severely diseased vines collected and preserved from the previous 
year. The artificial inoculations were made by atomizing the plants 
from three to five times during the season under moist weather con¬ 
ditions, with combined spore suspensions from pure cultures of the 
different biologic forms of Colletotrichum lindemuthianum and with 
bacterial suspensions of the blight organism. No separate inocula¬ 
tions with the biologic forms of anthracnose were undertaken in the 
field. 
In an acre portion of the 1923 East Lansing plot the most resistant 
varieties and selections discovered during the preceding years were 
segregated and given an unusually severe test. Following the 
method employed by Burkholder and Emerson of Cornell infected 
seed of very susceptible varieties were planted in “buffer” rows 
spaced about 12 inches from the supposedly resistant type to be 
tested. Abundant infection was further secured in this plot by the 
aid of oscillating sprinklers and by cheesecloth inoculation cages kept 
continuously moist by properly directed spray nozzles (pi. 1). 
The bacterial-wilt inoculations, limited to preliminary tests in the 
summer of 1923, were made both on young seedlings and on tender 
growing parts of older plants. Ten plants of each variety were 
inoculated when 8 to 12 days old by simply jerking off one or both 
of the shrunken cotyledons prior to formation of the abscission layer 
and applying a drop of bacterial suspension from a 3 to 4 day old 
potato cylinder culture. The figures in the eleventh column of 
Table II give the results of these tests. The first series of inoculations 
on older plants was made when the plants were approximately 
3 weeks old. The bacteria were pricked into the young growth, 
stems, petioles, and runners, at 2 or 3 different parts of the plant, 
with a flamed needle. Since after 10 days but few of the varieties 
showed evidence of infection, a second attempt was made, in which 
not only the young growing parts but also the main stems were 
inoculated. A large number of the varieties still remaining unin¬ 
fected up to the flowering and podding stage were inoculated a third 
time in the same way, but agam without much success. As shown 
later the “cotyledon method” was found much more certain of 
securing constant and uniform infection and was much quicker, but 
the period in the growth of the plant during which it can be carried 
out is too short to permit inoculation of a large number of varieties. 
It should be done only during the stage of growth indicated, since 
removal of the cotyledons too early is obviously injurious to the 
plant, and after the abscission layer is formed the vessels in which 
the bacteria enter are of course closed. 
