18 BULLETIN 64, U. S. DEPARTMENT OF AGRICULTURE. 
trouble here described as "curly-dwarf 1 (Kjauselkrankheit) . He 
emphasizes the rolling of the leaves, but does not mention that they 
wilt. The discoloration of the vascular bundles of stem and tuber 
is remarked, and experiments are cited which show that the disease is 
transmitted through affected seed tubers. 
The same author (1912) further illustrates the distinction between 
curly-dwarf (''curl") and leaf-roll, and reports having found cases 
of leaf-roll in which no Yerticillium or other fungus was present. 
Tubers from such plants gave rise to healthy plants, whence it is 
concluded that the occurrence of the true leaf-roll in Ireland is not yet 
established. 
These facts, together with his personal observation in Great 
Britain in 1911, led the writer to believe that no cases of true leaf-roll 
or of Fusarium wilt have yet been proved to occur in Great Britian, 
but that VerticiUium wilt is not uncommon there. 
Some confusion still remains concerning the parasitism of Verticil- 
lium albo-atrum, inasmuch as there are many reports of its occurrence 
where the marked pathological effects here described were not present. 
Keinke and Berthold report successful inoculations, and Wolienweber 
obtained infections in Friedenau, Berlin, which, in the light of his 
later work, are to be considered as added evidence of the parasitism 
of this species. The result of a later successful infection experiment 
performed by Wolienweber with pure cultures in the Washington 
greenhouse is shown in Plate III. The parasitism of Verticillium on 
other plants has also been demonstrated by him and will soon be 
published in full. It is not to be understood that the relatively minor 
role now played by Verticillium as a potato parasite in the United 
States indicates that it is a disease that should not be feared, for, if 
control measures are neglected, it might easily become epidemic and 
as destructive as the Fusarium wilt. 
The disease should be easily brought under control, however, by 
seed selection and rotation of crops. Whenever a wilted hill is 
observed in a field it should be taken up and both vines and tubers 
carried out and destroyed. When cutting seed, any with a brown 
stain at the stem end should be rejected. When a field is much 
affected by this trouble, none of the crop should be used for planting, 
and the ground should be given a longer rotation than usual. 
LEAF-ROLL. 
LITERATURE OF THE DISEASE. 
No plant disease in this generation has been the subject of such 
general discussion as that known in Germany as the "Blattroll- 
krankheit," herein named "leaf-roll." None has aroused greater 
difference of opinion as to its nature and cause, and no other single 
malady of plants is to-day receiving so much investigation by skilled 
