450 ALLARD: MOSAIC DISEASE OF TOBACCO 
peculiar property of engendering a similar diffusible toxin within 
the cells. In some respects Hunger’s toxin theory is not far re- 
moved from Beijerinck’s ‘‘contagium vivum fluidum”’ theory. 
Hunger remarks that the Deli-Sumatra tobacco, through inten- 
sive breeding, has become especially subject to mosaic. He men- 
tions that soils most favorable to the production of the best type 
of Sumatra tobacco are also especially favorable localities for 
mosaic, while on ‘‘paja-soil’’ which produces the most inferior Deli 
wrappers, mosaic is almost unknown. 
In 1908 Clinton (53), working in Connecticut, established an 
important fact concerning the mosaic disease. By artificial in- 
oculation he showed conclusively that the mosaic disease of tobacco 
was communicable to healthy tomato plants and vice versa. 
This seems to be the first actual proof that this disease of tobacco 
is infectious to plants of other solanaceous genera. 
Lodewijks (56), in 1910, reported his investigations concerning 
the effects of different kinds of light upon the development of the 
mosaic disease. By keeping the upper diseased portions of mosaic 
plants covered while at the same time the lower, healthy-appearing 
leaves were exposed, Lodewijks claims to have obtained remark- 
able results. Under these conditions he claims to have found that 
diffused light checked the disease, red light decreased it, and blue 
light completely cured plants of the malady. It was his opinion 
that an antivirus or antitoxin was thus formed in the lower, 
healthy leaves which destroyed or rendered inert the virus of the | 
disease. These results are so radical that further investigation 
seems necessary in order to understand their meaning more 
fully. | 
In 1910 Westerdijk (57) published an account of the mosaic 
disease of tomato. She concludes that this disease is infectious to 
tomatoes, but that it is not communicable to tobacco. She like- — 
wise believes that the development of the disease is greatly de- 
pendent upon the intensity of light, strong sunlight increasing the 
intensity of the symptoms. In striking contrast to the mosaic 
disease of tobacco, she claims that the mosaic disease of tomato 
is carried to the next generation through seed produced by mosaic 
plants. Westerdijk stated that she was unable to communicate 
the mosaic disease of tobacco to healthy tomato plants by artificial 
