528 
Journal of Agricultural Research 
Vol. XXX, No. 6 
the natural spread of rugose mosaic and 
leaf-rolling mosaic with the appearance 
of current-season symptoms. These 
include spotting, streaking, and leaf 
dropping, which also may result from 
delayed symptoms or incomplete infec¬ 
tion which sometimes follow tuber per¬ 
petuation. 
(12) Ninety healthy seedlings were 
grown from seeds produced by several 
Green Mountain plants, although the 
parent plants either were affected with 
mosaic or had mosaic tuber progeny. 
(13) Mild mosaic Bliss Triumph sister 
hills (from the same seed tubers) planted 
in three regions showed less distinct 
mottling in Virginia but contracted more 
rugose mosaic, leaf-roll, and spindle 
tuber there than on Long Island and 
contracted least of all in northeastern 
Maine, as shown by the progeny all 
grown in northeastern Maine. 
(14) Comparatively healthy commer¬ 
cial stocks of five varieties divided and 
grown in four regions mostly next to 
diseased rows, with the progeny all 
grown in one place, showed that mild 
mosaic spread more in Virginia and on 
Long Island than in southwestern and 
northeastern Maine; that rugose mo¬ 
saic was contracted markedly in Vir¬ 
ginia but not elsewhere; that leaf-roll 
spread more farther south; that spindle 
tuber increased more in Virginia than 
elsewhere; and that the total disease 
percentage increased most in Virginia 
and least in Maine. It is therefore 
concluded that a hot climate may cause 
degeneration of potatoes indirectly 
through favoring the spread of diseases. 
It also suggests why northern-grown 
seed is preferred; how buyers and sellers 
of seed if from different regions may 
misunderstand each other in discussing 
“mosaic/’ because of familiarity with 
different types; and why the potato de¬ 
generation problem requires local or 
regional study. 
