28 BULLETIN 64, IT. S. DEPARTMENT OP AGRICULTURE. 
from whom so much has already been drawn, the ones deserving of 
special mention are those of Dr. Schander 2 in the" Kaiser Wilhelms 
Institut fur Landwirtschaft in Bromberg and of Dr. Spieckermann 
in Muenster. So man}^ others have written on this subject that it is 
possible only to refer to the extensive bibliographies of Appel and 
Schlumberger, 1911, of Kock and Kornauth, 1911 and 1912 
(Mitteilungen des Komitees zum Studium der Blattrollkrankheit, 
Nos. 2 and 5), and of Himmelbaur, 1912. 
GEOGRAPHIC DISTRIBUTION OF LEAF-ROLL. 
Much is lacking in the knowledge of the exact distribution of the 
leaf-roll diseases, but it begins to appear that it is now, or soon will 
be, a factor in potato culture wherever this crop is grown. Its 
occurrence is certain in Germany, Austria-Hungary, Switzerland, 
the Netherlands, Denmark, and Sweden, as well as in the United 
States. It is probably in Norway, Russia, Bulgaria, and Roumania. 
That it has not been reported in France, Belgium, and England may 
be because of lack of sufficient observation. The somewhat limited 
observations of the writer in these countries in 1911 failed to disclose 
&rj true leaf-roll. The disease reported under that name from 
Ireland is the Verticilhum wilt. 
In Germany the leaf-roll has been most widespread and injurious 
in the west, e. g., in Westphalia and the Rhine provinces, though 
since its first outbreak in 1905 the introduction of healthy seed stock 
from other districts is reported to have restricted its spread. Leaf- 
roll has been observed in nearly all parts of Germany, but in most 
cases only scattered fields suffered. 
In Austria, also, the disease seems to be present in nearly all dis- 
tricts, including Hungary, though not always to a destructive degree. 
OCCURRENCE OF LEAF-ROLL IN THE UNITED STATES. 
Two developments of leaf-roll in this country have been studied 
hy the writer. One was in a collection of seedlings grown by Prof. 
Wilham Stuart, of the Bureau of Plant Industry, and the other was 
a destructive outbreak in eastern Colorado and western Nebraska 
during 1911 and 1912. The leaf -roll in the seedling collection, while 
not of direct economic importance, afforded an opportunity to 
diagnose the trouble and differentiate it from others and also sug- 
gested a probable solution of the problem of control. 
The western outbreak was, on the other hand, the cause of immense 
losses and brought the leaf-roll problem, for the first time, to the 
forefront in this country. That it will continue to be an important 
economic factor in American potato production is indicated by its 
discovery in two new localities in 1913. The writer found a field of 
Irish Cobbler near Onley, Va., with well-marked leaf-roll character- 
ized by rolled leaves with a reddish tinge and stunted growth. The 
