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 

 dro]3 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 assimilati^^e 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. 



Where 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 frequentl}^ 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 



