June, 1913.] 
The Mosaic Disease of the Tomato. 
153 
Westerdijk (1910, p 7) states, “a great share of the blossoms 
perish before fertilization is effective; either the flowers blight or 
drop off. ” She also states that diseased plants bear less fruit 
than normal and that the fruit which does set is usually small 
or malformed. This would naturally be expected where there 
is an apparent lack of proper nutrition, brought about perhaps 
by a reduction in the assimilative and digestive powers of the 
leaves. 
It often happens that some of the lower leaves of tomato 
plants show yellow spots or are entirely yellow; this in most 
cases is due to improper light or soil conditions and should not 
be mistaken for mosaic disease. 
Fig. 1. Leaves from various parts of mosaic-diseased potato plants, 
showing surface irregularities, due to variable tissue expansion. Two- 
thirds natural size. 
AVhere tomatoes are grown under glass, the extent of damage 
caused by this disease may vary from the injuring of a few scattered 
plants to the loss of a considerable share of the crop. In Ohio 
mosaic disease frequently appears in one or more of the main 
crops. 
Potato .—During the month of February, 1913, mosaic disease 
appeared very suddenly in the Ohio State University greenhouse, 
on Early Lunch potatoes, which had been planted in sand for 
