448 ALLARD: MOSAIC DISEASE OF TOBACCO 
a long time was confused with ‘‘ Mosaikkrankhei¢c.’’ Although he 
believed that the mosaic disease was a physiological disturbance 
\ arising from unfavorable conditions, Hunger held that an un- 
organized ferment of the toxophore group of Oppenheimer, rather 
than oxidizing enzyms, was responsible for the appearance of the 
_ disease. 
In 1905 Jensen (47) published a paper in which he mentioned 
the different means by which the occurrence of mosaic could be 
lessened according to the views of various invescigators, 1. e., 
Mayer, Raciborski, Woods, Sturgis, Koning, Hunger, and others. 
He stated that since these workers regarded the soil in some way 
responsible for the origin of the disease, their attention was 
direcced mainly to the treatment of the soil of the seed bed and the 
field. For the seed bed, sterilization, soil-removal, and the use of 
certain kinds of manures were generally recommended. For the 
prevention of the disease in the field, certain fertilizers were 
advised. Sturgis, in Connecticut, was inclined to believe that the 
use of shade lessened the occurrence of mosaic, Woods also con- 
sidered that injury of any sort predisposed the young plants to 
the disease. For this reason he considered that root injury must 
be guarded against during transplanting, in order to reduce the 
amount of the disease in the field. 
Jensen first reviews somewhat critically the methods employed 
by Sturgis, Iwanowski, and Hunger to show that the seed of mosaic 
mother plants produce healthy progeny. He describes in detail 
the results of special selection experiments which he carried on 
in Java with mosaic and healthy plants. He made careful com- 
parison of the progeny of one self-fertilized healthy plant as a 
control and four mosaic plants grown side by side under identically 
the same conditions from the seed bed to the field. The percentage 
of mosaic plants occurring in each progeny was separately deter- 
mined. Without exception mosaic plants appeared in every 
progeny in varying amounts. 
From these experiments Jensen is inclined to believe that the 
progenies of the mosaic plants show greater susceptibility to 
mosaic than the progeny of the healthy plants, and that the 
careful selection of resistant races will prove to be a practical 
method of controlling the disease. However, from the amount of 
