958 
Journal of Agricultural Research 
Vol. xxni, No. xa 
to the degree to which it was masked. The vines, especially at Duluth, 
Grand Rapids, and Crookston, were usually killed by frost before the 
ripening period was completed, so that the stage of maturity probably 
influenced the color appearance of the tuber. The type of soil at a 
particular place also had a noticeable effect on the skin, as, for instance, 
tubers grown in sandy loam soil at Grand Rapids possessed a flakiness 
of skin whereas those grown at Duluth on clay soil containing a plentiful 
supply of humus were extremely smooth. A similar smoothness was 
obtained on tubers of the same stock when grown on peat at the Coon 
Creek Peat Experimental Farm at Anoka. These and other factors 
which influence the texture and quality of the skin were probably the 
cause of some of the difference in the color of the tubers. 
CONCLUSION 
The lots of Early Ohio potatoes were, as far as could be ascertained, 
identical in their characteristics. The number of lots under observation 
was relatively small. It must, however, be considered that each lot 
was chosen because it offered a possibility of being a distinct strain. 
Furthermore, two of the seed stocks were known to have been separated 
from each other and from the other seed stocks studied for at least 20 
years. As the Early Ohio originated approximately 50 years ago, 20 
years would seem to be sufficient time to allow strains to develop within 
the seed stocks of a variety, if such a tendency existed. The selection 
practiced by the growers with divergent types in view should further 
have tended to bring out any differences that might have developed. 
Also the difference in environment was sufficiently great to bring out 
distinct differences in the expression of characters studied. If the 
environment had any tendency to influence the expression of the char¬ 
acter in the progeny, its influence should have been apparent at the end 
of this period. The evidence presented indicates that the potato variety 
is relatively stable under vegetative propagation. While mutations are 
known to occur, they are apparently not sufficiently numerous to offer 
reasonable hope for the further improvement of varieties by asexual 
selection. This does not mean that the methods of asexual selection 
are of no value in the improvement of commercial seed stocks. The use 
of the individual-hill and tuber-unit methods of asexual selection in the 
seed plot aid in the elimination of varietal mixtures, and by separating the 
progeny of diseased and healthy tubers in the seed plot are of aid in 
the roguing out of diseased plants. 
SUMMARY OF EXPERIMENTAL RESULTS 
(1) Seven lots of Early Ohio potatoes representing difference in 
amount of selection practiced by growers and distinct regional types 
were obtained from growers at Anoka, Duluth, Grand Rapids, Glyndon, 
Hawley, Faribault, and Hopkins, Minn. Observations were made on 
the behavior of the lots in 1917, when grown in comparison with each 
other at University Farm, Duluth, Grand Rapids, and Crookston. 
In 1918 the lots were under observation at two or more places. On 
some lots observations were continued in 1919 and 1920. 
(2) In 1917 there was a difference of 20 bushels per acre between 
the average yield at the four places of the highest yielding and lowest- 
yielding lot. No lot consistently gave either a high or low yield at more 
