16 BULLETIN 64, U. S. DEPARTMENT OF AGRICULTURE. 
It is the writer's opinion that under present conditions this is not 
a quarantinable disease. It is very widely distributed in the United 
States, as already shown. It would be difficult to establish the 
boundaries of infected areas, and almost impossible to apply quaran- 
tine restrictions without serious injury to commerce. Nor is it 
certain that the aim desired would be accomplished in this way. 
There are so many avenues for the spread of plant diseases that it 
often seems as if only ocean barriers were of avail. (Lounsbury, 
1909, 1910.) 
OCCURRENCE OF AMERICAN FUSARIUM WILT IN EUROPE. 
The bulletin by Smith and Swingle had its influence on European 
pathology, inasmuch as the leaf-roll epidemic, which began in 1905, 
was at first believed to be a Fusarium disease. The fact that none 
of the European workers had seen the American disease and that no 
American pathologist familiar with wilt had seen the leaf-roll in 
Europe led to further confusion. 
The writer now believes that there is no evidence that the American 
wilt disease occurs in Europe. This statement is based on observa- 
tions made in the course of a study trip through Germany, Austria, 
and England in 1911. No cases of typical Fusarium wilt were seen. 
Furthermore, Dr. Wollenweber, in the morphological studies later 
mentioned, has been able to differentiate the Fusarium oxysporum of 
Smith and Swingle from other potato Fusaria, and he finds this to be 
distinct from any European form. Inasmuch as he studied critically 
the Fusaria isolated from leaf-roll material while at Dahlem, Berlin, 
this result is very significant and goes far to explain the difficulty 
German workers have had in verifying the observations of Smith and 
Swingle. Himmelbaur (1912) reports Fusarium to occur in much of 
the leaf -roll material studied by him in Austria, but he has not 
identified the species, and until this is done his results can not be 
correlated with the results of American workers. 
VERTICILLIUM WILT. 
DESCRIPTION OF THE DISEASED PLANTS. 
The Verticillium wilt of potatoes is characterized by a wilting or 
blighting of the foliage, resulting in the premature death of the hill. 
The vascular bundles of the stem, the stolons, and usually of the 
tubers, are filled with the mycelium of Verticillium alho-atrum. The 
spores of this fungus often cover the dead stalks, so that they 
become conspicuous from their gray color. 
As observed by the writer in this country and in England in 1911, 
plants attacked by Verticillium wilt generally die quickly. There 
may be yellowing of the foliage, but the drooping and wilting has 
been pronounced in most of the cases observed. The Verticillium wilt 
