106 
Journal of Agricultural Research 
Vol. XXX l. No. 2 
GREENHOUSE STUDIES 
The greenhouse inoculation tests were conducted during the 
winters of 1922-23 and 1923-24 at Arlington Experiment Farm, 
near Rosslyn, Va., and were limited to anthracnose and bacterial 
wilt. Although considerable time has been given the problem, the 
writers have thus far failed to develop a satisfactory greenhouse 
method for obtaining quick and conclusive evidence on the relative 
susceptibility of varieties in the seedling stage to bacterial blight. 
Since most of the American varieties have been tested by Barrus 
( 1) for their separate reaction to the alpha and beta biologic forms 
of the anthracnose organism, principally foreign varieties were 
included in the authors' greenhouse studies. These were inoculated 
separately with the alpha form, and on account of the great similarity 
of the beta and gamma forms, as shown by the work of Burkholder 
{2) , the comparative unimportance of the gamma form and limitations 
in greenhouse space these two forms were usually combined. All 
of the eight Minnesota forms were likewise combined, and to these 
were added in one inoculation (reported in Table III) the above- 
mentioned three forms from Cornell, the object being to obtain a 
control on the field results and, as already mentioned, to find varie¬ 
ties resistant to all known forms. 
The different lots were planted in fresh loam soil in regular green¬ 
house benches with the sides raised 6 inches above the soil in order 
to turn them into moist chambers after inoculation by covering with 
wet burlap-lined coldframe sashes (pi. 2, A). Ten seeds of each 
variety were spaced 2 inches apart in short rows extending crosswise 
in the bench, and in every tenth row controls known to be susceptible 
to the biologic form being tested were planted. White Navy and 
Boston Pea were used most frequently for controls on alpha , Im¬ 
proved Golden Wax and ordinary Red Kidney for beta , and Well's 
Red Kidney, White Imperial, and Nova Scotia Marrow for gamrna . 
The differential varieties and strains used as controls on the Min¬ 
nesota biologic forms were planted in small pots and inoculated 
separately with each form in another greenhouse and then returned 
to spaces left yacant in the bench among the varieties to be tested, 
which in the meantime had been sprayed with a combined spore 
suspension of all the forms. In this way one could make sure that 
all cultures were virile and acting upon the varieties under the 
conditions of the test. The plants were inoculated as soon as possible 
after germination and kept moist by aid of the wet covering for 48 
hours. The temperature ranged from 18 to 20° C. for the first few 
days, but later often went much higher. The results were recorded 
in all cases 10 days after inoculation. Plate 2, B is a typical illustra¬ 
tion of the decisive outcome of experiments of this sort. From the 
above description it is seen that the temperature, time, and other 
conditions followed closely the standardized and very satisfactory 
procedure originally used by Barrus ( 1 ) and subsequently confirmed 
by the infection studies of Lauritzen (7). 
The greenhouse wilt inoculations were made on plants grown in 
benches as above described and generally by the “ cotyledon 
method." The temperature was held at about 25° C., and notes 
on permanent wilting of one or more of the first trifoliate leaves, as 
illustrated in Plate 3, B, were made one, two, and three weeks after 
