486 
Journal of Agricultural Research 
VoX. VII, No. IX 
tobacco. Likewise, she could not infect tomato plants with the sap 
of a mosaic disease of tobacco with which she worked. 
The constancy of these negative results is rather striking. It is 
possible that the type of mosaic disease with which European investi¬ 
gators worked may not have been quite so readily communicable to 
plants of other species and genera of the solanaceous family as the type 
in the writer’s possession. It has been more or less generally believed 
in Europe that N. rustica was even immune to the mosaic disease affecting 
tobacco. In the writer’s experience the virus of the common form of the 
mosaic disease is not only very infectious but particularly malignant to 
plants of N. rustica . Likewise, the disease is readily communicable to 
all the more distinct varieties of tomatoes, petunia, Datura stramonium , 
and is highly infectious to Hyoscyamus niger. 
PLATE 35 
Leaves of Nicoiiana viscosum affected with the mosaic disease. This mosaic disease 
does not affect ordinary tobacco ( N. tabacum); nor does the mosaic disease affecting 
ordinary tobacco affect N. viscosum. 
