4 BULLETIN 64, U. S. DEPARTMENT OF AGRICULTURE. 
In the same year there occurred in eastern Colorado, western Nebraska, 
and adjacent districts a very serious outbreak of a potato disease 
which was at the time locally attributed to Fusarium (Fitch, C. L., 
in numerous newspaper articles). 
The many discrepancies and confused points in the description of 
these diseases as presented in the European literature, in comparison 
with American conditions, were further cleared up by the study 
in 1912 of disease phenomena in a collection of seedling varieties 
grown in Maine and New York by Prof. William Stuart, of the 
Bureau of Plant Industry. Pure types of several of these troubles 
were presented, thus greatly facilitating their diagnosis and differ- 
entiation. 
A visit to several other potato centers in Wisconsin, Minnesota, 
Colorado, Utah, Idaho, and California assisted in verifying the con- 
clusions reached, which are given in detail in this bulletin. 
Briefly stated, it appears that several distinct diseases have been 
confused to a greater or less degree by both American and European 
writers, and the widely differing opinions and results are due to the 
fact that none of the investigators had seen conditions in all the 
countries. In particular, the American and European troubles had 
not been compared. 
In the present article several types of disease are to be distin- 
guished as of some importance, at least in the United States, viz: 
Fusarium wilt. — A disease characterized by the wilting or prematuring of the 
plant, accompanied by a browning of the vascular bundles of stem and tuber, which 
are infected by Fusarium oxysporum (Schiecht) Sm. and Sw. Widespread in 
America, but not yet identified from Europe. 
Vertidllium wilt. — A wilt resembling the foregoing, often more rapid and with 
fungus mycelium higher in the stem. Due to Vertidllium albo-atrum Reinke and 
Berth. Described by Reinke and Berthold in 1879. Present in both America and 
Europe. 
Leaf-roll. — An inheritable disease marked by rolling of the leaves, reduced yield, 
and other symptoms. Probably not due to a parasite. Common in Europe and 
lately appearing in America (Blattrollkrankheit). 
Curly-dwarf. — An inheritable, nonparasitic trouble in which dwarfing of the vascular 
elements is a prominent characteristic. Found in Europe and America (Krau- 
selkrankheit). 
Rosette. — A stunted or dwarfed condition of the potato associated with injuries 
of the underground stems and roots caused by the fungus Rhizoctonia; most con- 
spicuous in the western United States. 
Mosaic. — A pathological condition marked by a mottling and distortion of the 
foliage. Not previously described, but present in Europe as well as America. 
It is not unlikely that future studies will enable us to add still 
other diseases to this group, and it may become convenient to differen- 
tiate more types of leaf-roll and of curly-dwarf from within the rather 
wide limits established in this paper. 
The disease described by Appel as bacterial ring disease should be 
mentioned. It appears that in Germany this was formerly confused 
