Mar. 24,1923 
Permanence of Variety in the Potato 
957 
throughout the season. When growth conditions are such as to cause 
a second growth of the plant, the formation of knobs frequently occurs 
on the tubers of some varieties. In the original lots of Early Ohio 
secured in the spring of 1917 all were comparatively free of knobs except 
lot 8. Traces of knobs had formed on all but lot 2. The progeny of 
these lots when examined in the fall of 1917 were found to be similar 
for this character in all lots grown at the same place. Knobs were 
present to a greater or lesser degree on the tubers of the lots grown at 
Grand Rapids, University Farm, and Crookston. Those grown at 
Duluth were free of knobs. In 1918 all lots at University Farm pro- 
duced knobs, while at Duluth, Grand Rapids, and Crookston potatoes 
were free of knobs. The six lots appeared to give a similar reaction in 
regard to the formation of knobs under similar environmental conditions. 
Another undesirable character is the formation of fissures or crevices 
on the surface of the tubers. The tubers of the original lots of Early 
Ohio were free of these fissures. Tubers containing fissures were fre¬ 
quently found in all lots grown at University Farm in 1917 and 1918. 
In 1917 they were occasionally found in tubers of lots grown at Crookston. 
At no time were fissures found in tubers of lots grown at Duluth and 
Grand Rapids. 
The depth of eyes and prominence of eyebrows were found to be simi¬ 
lar for the progeny of all lots grown at the same place. Distinct differ¬ 
ences in the expression of these characters were produced at the different 
places, but this difference in expression had no influence on the progeny* 
as the characters were again expressed according to the environmental 
conditions under which the tubers developed. 
The surface of the skin of the Early Ohio tuber is covered with small 
corky dots or lenticels. De Vries (23) has shown that the lenticels on 
potato tubers are due to the growth of loose cells underneath the stomates* 
which push up through the stomates and rupture them. He pointed 
out that a prominent development of them could be secured by having 
the tuber under moist conditions. These dots either do not occur at 
all or are relatively inconspicuous on varieties belonging to the Rose 
group. The original lots differed in the number and prominence of 
these lenticels on the tubers. The lenticels were very prominent on 
the progeny of all lots grown at University Farm in 1917, slightly less 
prominent on those grown at Crookston, slightly prominent on those 
grown at Grand Rapids, and very inconspicuous on those grown at 
Duluth. The result was similar in 1918. 
In the original seed stocks the tuber color was distinctly different for 
each lot. The difference did not reappear in the progeny of the lots 
when grown under similar conditions. The growth conditions at each 
place produced a characteristic color of tubers. At times there ap¬ 
peared to be a difference between lots grown at the same place, but no lot 
was consistently different from the others in this respect. There was 
always considerable variation between individual tubers of the same 
lot. In general the larger tubers appeared less colored than the smaller 
ones. The color in the tuber of this variety is in the tissue directly 
beneath the cells forming the outer skin. De Vries (23) called atten¬ 
tion to the fact that in the last growth of the skin dining the ripening 
period the skin, which is previously clear, transparent, and smooth 
becomes thick and opaque. In the lots of Early Ohio under observa¬ 
tion the difference in the amount of color present may have been due 
