THE MOSAIC DISEASE OF TOBACCO. 25 



material, consisting of stem and leaves, was finely chopped into the 

 soil and covered with a shallow layer of fine soil. Others, serving 

 as controls, were given the same soil preparation without the addi- 

 tion of plant material. These frames were kept carefully screened 

 until the plants outgrew them. As soon as the young plants ap- 

 peared fumigations with nicotine were made from time to time to 

 prevent infestation by aphides. The size of each frame, the amount 

 of green mosaic stems and leaves chopped into the soil, and the 

 occurrence of the mosaic disease in each are shown below. The 

 plants were kept under observation at all stages of development until 

 the close of each test. 



Frame No. 1, control, 18 inches square ; nothing put into the soil ; seed sowed 

 August 9. When examined on October 6 the plants were growing vigorously 

 and all were healthy. On December 9 the plants, 36 in number, were 2 feet 

 tall, mostly in bloom, and all healthy but one, which had developed the mosaic 

 disease. 



Frame No. 2, 18 inches square ; 2,000 grams mosaic stems and leaves chopped 

 into the soil ; seed sowed August 9. On October 6 the plants were larger, of a 

 darker green, and more thrifty than the control frame No. 1. They were 12 

 to 13 inches high and badly crowded, conditions probably due to the fertilizing 

 effect of the decomposed plant material originally added to the soil. When 

 examined on December 9 the 45 plants were 3 to 4 feet high and many were in 

 bloom ; all, from the smallest to the largest, were free from disease. 



Frame No. 3, control, 18 inches square ; nothing added ; seed sowed August 9. 

 On October 6 the plants, 30 to 35 in number, were 7 to 8 inches high, dark 

 green, and free from disease. When examined again on December 9 the plants 

 were 2 to 4 feet high, many were in bloom, and all were free from disease. 



Frame No. 4, 18 inches square ; 3,000 grams of green mosaic stalks and leaves 

 chopped into the soil ; seed sowed August 20. On October 6 the plants, although 

 thickly crowded, were 4 to 5 inches high and very green and healthy. Not a 

 single case of mosaic disease was evident. On December 9 the 75 plants aver- 

 aged 2 to 2J feet high, growing under badly crowded conditions; many plants 

 were budding. No mosaic disease appeared. 



Frame No. 5, 18 inches square; 2,500 grams of mosaic material added to the 

 soil; seed sowed August 20. On October 6 the plants were 3 to 4 inches high 

 and badly crowded; none diseased. On December 9, 30 plants were counted; 

 all were about 2 feet in height and preparing to blossom ; none diseased. 



Frame No. 6, control, IS inches square ; nothing added to the soil ; seed sowed 

 August 20. On October 6 the plants, although crowded badly, were 3 to 4 

 inches high and free from disease. On December 9 the plants, 45 in number, 

 were about 2 feet high and just ready to bloom ; none diseased. 



Frame No. 7, 10 inches square; 1,230 grams of green mosaic material added 

 to the soil; seed sowed August 19.<»On October 6, 40 to 50 plants, averaging 

 4 to 5 inches high, were growing in this space; badly crowded, yet none dis- 

 eased. On December 9 there were 35 plants, ranging from 6 inches to 3 feet 

 8 inches high. The largest plants were in bloom; others were budded; no 

 disease developed. 



Frame No. 8, control to frame No. 7, 10 inches square; nothing added; seed 

 sowed August 19. On October 6 the plants were about 3 inches high and all 

 healthy. On December 9 these plants were still free from disease, and their 

 average height was 18 inches, a few reaching the maximum height of 2 feet. 



