256 
Journal oj Agricultural Research 
Vol. XXV, No. 6 
sions closely duplicate and corroborate those of the present investigation. 
This is notably true of the correlations shown between spindling-sprout 
and net-necrosis of the tuber and leafroll of the foliage. In addition to 
these correlations, the studies reported herein furnish evidence on other 
matters related to tuber germination and foliage symptoms—namely, 
(a) retardation in the sprouting of mosaic and leafroll tubers, (b) bud uni¬ 
formity in mosaic and leafroll tubers, (c) the simultaneous occurrence of 
both mosaic and leafroll symptoms in the same plant, ( d ) variation in the 
progressive seriousness of mosaic infection from season to season, and ( e ) 
apical dominance in its relation to disease. 
GERMINATION TESTS 
During the winters of 1919-20 and 1920-21 many tubers of known 
history as to the condition of the plants from which they came were 
germinated. The germinations were made in the greenhouse under fa¬ 
vorable conditions of moisture and temperature, the seed pieces being 
planted in soil in benches and pots or in sawdust and excelsior in wide 
shallow pots. In the course of the trials it was found that tubers from a 
crop planted in May and harvested in October did not germinate normally 
until the following January or February. In the length of the rest 
periods thus indicated the facts observed conform m general to the ob¬ 
servations of Appleman (2), who found that the rest periods of Irish 
potatoes differed to some extent between varieties but were quite uniform 
within a certain variety. He found that while in general the rest period 
was terminated after about 90 days, it could be very much shortened by 
removing the skins from the tubers without injury to the buds. In the 
course of the investigations herein reported, earlier germination was se¬ 
cured by using Appleman’s method, which, however, did not prove to be 
adapted to the needs of the present studies. The most satisfactory re¬ 
sults were secured from germinations made toward the end of the storage 
season, during February, March, and April, while some of the most sig¬ 
nificant observations on spindling-sprout were made in the case of tubers 
sprouting in the storage cellar at the very end of the storage period. 
The cellar in which the tuber samples were kept during the winter was 
sufficiently moist so that the potatoes did not shrivel, and registered tem¬ 
peratures ranging from 35 to 45 0 F. throughout the winter months, rising 
with the higher temperatures of April and May. At planting time most 
of the tubers had developed sprouts of varying lengths. 
RETARDATION IN SPROUTING 
As a result of germinating many tubers both diseased and healthy 
in the greenhouse, evidence has accumulated that germination of the 
seed piece and growth of the young shoot are definitely and markedly 
retarded both in the case of serious mosaic and of serious leafroll infec¬ 
tions. In instances of mild degrees of infection, however, little if any 
variation from the normal appearance in sprouting can be detected. In 
order to secure evidence on this point, tubers of the Green Mountain 
variety were used, some of them of known history as to the presence 
or absence of disease for one or more seasons, while others were derived 
from general stock. One half of each tuber was planted in a shallow 
pot on moist sawdust and covered with excelsior, and the other half 
was planted in soil in an 8-inch pot. All were given uniform treatment 
as to light, moisture, and temperature. The appearance and rate of 
