8 BULLETIN 1361, U. S, DEPARTMENT OF AGRICULTURE 
Table 1. — Results obtained with seedlings of Harvest Queen and Currell winter 
lolieat and Wisconsin Pedigree No. 2 winter rye uninoculated and inoculated 
with juice and pulp from mosaic-infected Currell wheat 
Experi- 
ment 
"Variety 
Total 
num- 
ber of 
plants 
Inoculated 
or control 
Number of mosaic-infected 
plants 
Without rosette 
To- 
tal 
With 
cell in- 
clusions 
With rosette 
To- 
tal 
With 
cell in- 
clusions 
Number of 
healthy plants 
To- 
tal 
With 
cell in- 
clusions 
No. 1 
No. 2 
No. 3 
No. 4 
No. 5 
No. 6 
No. 7" 
[Harvest Queen. 
.—do 
Currell 
Harvest Queen. 
—.do 
Currell 
.—do 
Harvest Queen. 
— _do 
Currell 
--do 
Harvest Queen. 
---do 
Currell 
.—do 
Harvest Queen. 
_-_-do 
Currell 
---do 
Harvest Queen. 
_--do 
Rye 
-...do 
Harvest Queen _ 
__--do 
Currell . 
____do 
Rye 
.--.do 
Inoculated __ 
Control 
Inoculated- _ 
do 
Control 
Inoculated — 
Control 
Inoculated. _ 
Control 
Inoculated. _ 
Control 
Inoculated- . 
Control 
Inoculated- . 
Control 
Inoculated . _ 
Control 
Inoculated . . 
Control 
Inoculated.. 
Control 
Inoculated _ . 
Control 
Inoculated- - 
Control 
Inoculated. _ 
Control 
Inoculated. - 
Control 
° The wheat plants in experiment No. 7 were severely attacked by powdery mildew, and it was not 
possible to carry them for a sufficient length of time to obtain definite evidence on rosette. 
The fact that one infected Harvest Queen wheat plant in experi- 
ment No. 1 did not develop the rosette condition may be explained on 
a genetic basis. Head-selection studies indicate that varieties which 
may be homozygous for the ordinary botanical and agronomic char- 
acters are not necessarily homozygous for susceptibility to mosaic. 
This makes it necessary to make special selection studies within a 
variety in order to obtain homozygous material for the critical study 
of the disease. 
THE MOSAIC CAUSAL AGENT EXISTS IN CERTAIN SOILS 
So far as known, this is the first mosaic the causal agent of which 
is definitely known to be associated with soils. Experiments have 
shown that the causal agent of this disease persists in fine river silt 
(gumbo) soils for at least six years. Susceptible A r arieties of wheat 
never have failed to develop the disease when grown in infested 
gumbo or sandy clay soils out of doors. Field observations seem to 
