Apr. ax, X933 
Cultivated and Wild Hosts of Cane Mosaic 
257 
the varieties from Northern and Western States were conspicuously free 
from it. This result may be due in part to the fact that the northern 
and western varieties were subnormal in vigor. They were for the most 
part only half as tall as the southern varieites. It is now well known that 
a slight shortening of the accustomed length of day may check vegetative 
growth and hasten maturity in some varieties of plants (7), and this fact 
may account for the subnormal development of these varieties. It has 
been our experience that stimted plants are more difficult to infect 
experimentally than normal ones. The explanation for the low per¬ 
centage of infection in the varieties which were out of their proper 
environment may therefore be due to this fact rather than to any iimate 
character of resistance. 
A second experiment on a much larger scale with southern varieties of 
field com was started on May 15, one month after the first experiment. 
About 3 acres of corn, approximately equally divided among 17 varieties, 
was planted in a field immediately adjacent to badly diseased first 
ratoons of Louisiana Purple sugar cane. On July 15 the whole planting 
was carefully examined and a large proportion of all varieties was dis¬ 
covered to be already affected by the disease. The percentage of dis¬ 
eased plants on that date is given in Table VI. 
Tabl^ VI .—Results of tests for resistance to mosaic of varieties of southern field corn 
planted on May 15, ig2i 
Variety. 
Source of seed. 
Per¬ 
cent¬ 
age of 
mosaic 
on 
July 15. 
192X. 
Variety. 
Source of seed. 
Per¬ 
cent¬ 
age of 
mosaic 
on 
Jtily IS, 
Z93Z. 
]Mative ,.,, - - - 
Georgia. 
15 
Whatley Prolific. 
Georgia. 
40 
Pi>pe Prnlific. 
Florida. 
75 
Gerrick. 
South Carolina. 
5 ® 
XJ. S. Selection No. 165,. 
Texas.. 
30 i 
XJ. S. Selection No. 201.. 
Arkansas. 
60 
XJ. S. Selection No. 170,. 
. .do 
5 ® 
Cuban Yellow. 
Florida. 
45 
r^agiina. 
.do. 
24 
Station Yellow. 
Alabama. 
66 
Brazos. 
.do. 
40 
50 
Singleton. 
Texas. 
60 
ArtiTigtoTi Prolific; . 
Mississippi. 
XJ. S. Selection No. 230... 
Virginia. 
45 
Red Cob... 
.... do.. 
25 
Boone County (XJ. S. 
7 ® 
Millpond Prolific.... 
Georgia. 
8s 
Selection No. 1x9). 
A much higher percentage of infection was found in these plants than 
in the same varieties planted one month earlier. All of the com was 
heavily infested with Aphis maidis, but no other insect was noticeably 
abundant. 
In order to obtain data on the damage inflicted by this disease, 10 each 
of mosaic and apparently healthy plants in each variety were tagged for 
identification at harvest time. It is realized that many plants marked 
“healthy^' on July 15 may have become infected before harvest, so that 
any decrease in yield indicated by this method does not represent the 
real extent of the loss sustained. The loss due to mosaic is without 
question greater than that indicated by our data. All tagged plants 
with legible inscriptions were harvested on September 22, and the ears 
were examined and weighed. The number of ears, total weight, and 
average weight of ears of healthy and mosaic plants for each variety are 
given in Table VII. 
