BROWN ROT OF SOLANACEAE. 



I8 7 



July 14. Early Rose potatoes in the field (plants Nos. I to 120) were used for this experiment. The cultures used 

 were 5 slant agar-tuhcs of July 1 1 . from No. 4, March I (South Carolina) , slime washed off into distilled water 

 (150 c.c.). The inoculations were made near the top of the plants with a hypodermic syringe, 0.2 c.c. of the 

 liquid being put into each plant. The stems were very tender and soft. 



Result. First recorded signs on July 23, when 77 per cent showed signs, but they were slight for 9 days' incubation. 



July 16. Burbank potatoes in the field (plants Nos. 121 to 240) were inoculated in the same manner as the above, 

 using 6 slant agar-tubes of July 14, from No. I, March I ; slime washed off into distilled water (150 c.c ). 



Result.On July 25, 76 per cent showed signs of disease. 



July 22. Potatoes in the field (plants Nos. 241-480) were inoculated in the same manner as those of July 14, using 6 

 slant agar-tubcs of July 1 7, descended from No. i , March i ; slime washed off into distilled water ( 1 50 c.c.). 



Result. On July 27. 60 per cent showed signs of disease; almost no wilting. 



July 33. Potatoes in the field, half Early Rose, half Burbank (plants Nos. I to 240), were inoculated from 6 slant agar- 

 tubes of July 20, from No. 6, July 10 (descended from potato-stem from Norfolk, Virginia), employing the 

 method of inoculation used on July 14. 



Result. -On July 27, 96 per cent of the Early Rose and 89 per cent of the Burbank showed signs of disease. 



July 33. Early Rose and Burbank potatoes in the field half of each variety were inoculated (using plants Nos. 241- 

 480). The cultures were 6 slant agar-tubes, July 2 1 . from slant agar of July 20 from Virginia. The bacteria 

 were put on outside of stem with a hypodermic syringe, which was kept protected from the light ; the needle 

 was then passed through this liquid, and entirely through the stem, 10 pricks being made into each plant near 

 the top. No injection. 



Result. First signs on July 25. On August 3. 100 per cent showed signs of disease ; many were wilting and falling over. 

 There were also many 

 attacked by Fusarium 

 oxysporum (see Smith 

 and Swingle, Bull. 55, 

 Bureau of Plant In- 

 dustry. U. S. Dept. of 

 Agric., Feb. 16, 1904). 



July 38. Potatoes in the field 

 (plants 481 to 720), 

 half Early Rose and 

 half Burbank, were in- 

 oculated from 6 slant 

 agar-tubes of July 26; 

 slime washed off in dis- 

 tilled water. A little 

 liquid was drawn up 

 with a hypodermic 

 syringe wrapped in 

 black paper to protect 

 it from the light. This 

 liquid was put on the 

 stems and 10 needle- 

 pricks made through 

 it into the stems, with- 

 out injection. In all 

 of these large field 

 tests Mr. Deane B. 

 Swingle did the inocu- 

 lations and made the 

 counts. 



Result. On August 22, 96 per 

 cent of Early Rose and 

 94 per cent of the Bur- 

 bank were diseased as 

 a result of the inocu- 

 lations. 



July 27. Two tomato plants were inoculated from culture from No. i , July i (from tomato, South Carolina) with a 

 hypodermic syringe (0.2 c.c.). 



Result. The experiment was followed for many weeks. Adventive roots pushed out but the plants failed to wilt. 

 They grew luxuriantly after repotting, and bore fruit. 



March 17, 1904. Twelve plants of tomato (6 varieties), were inoculated from potato-cultures Nos. 2, 5, 8, March 14 

 (Virginia, isolation of 1903). The plants when inoculated were 4 weeks old, about 6 inches high, and had 3 to 

 4 leaves. Made 15 to 20 needle-pricks in leaf-blades. 



Result. No wilt ; plants grew well. The experiment was followed until May 10. 



April 16. Eight potato plants, 8 to 16 inches high, were inoculated from potato cultures Nos. I to 3 of April 13 (Vir- 

 ginia, 1903). Young internodes were pricked. 



Result. No wilt. The stems became very badly swollen and discolored (see vol. II, fig. 27). 



Fig. 95.' 



Fir,. 95. Cross-section of base of petiole of a potato-leaf, showing restriction of the bacteria (solid black masses 

 in center at right) to the vascular part. Plant No. 23, 1901 , inoculated from a pure culture of Bacterium solanacearum, 

 July 19, by needle-pricks. Material collected and fixed in strong alcohol on July 25, at which time the blade of the leaf 

 was badly shriveled. The shading between the cells in the outer part of the section represents collenchyma and not 

 bacterial occupation. Drawn under the Abbe camera with 8 mm. apochromatic objective and No. i compensating 

 ocular, from a paraffin section which was stained with carbol-fuchsin and washed in 50 per cent alcohol. Slide 123*. 



