1 84 



BACTERIA IN RELATION TO PLANT DISEASES. 



Result. Very successful (Bull. 12, pi. i, figs. 6, 7, and pi. 2, fig. 2). First signs appeared on third or fourth day; 

 weather hot, 28 to 32 C. The organism swarming in tissues of affected plants was a short, motile rod. 



June 23. Three old potato tubers and 3 cucumber fruits were used for these inoculations (4 inoculations, 2 checks). 

 The cucumbers were 7 inches long by 2 inches thick, green and firm. The potato tubers were large, smooth 

 and white, probably Burbank, kept under bell-jars. Same culture used as for inoculations of June 15. 



Result. The cucumber fruits rotted, but no plates were poured. In the worst injured potato the bacteria, which were 

 numerous along the line of the punctures, extended scarcely i mm. beyond; starch intact. 



July II- Two cucumber fruits under a bell-jar were inoculated from tube No. 4, July 8. 



Result. One of the fruits rotted, but no plates were poured. The bacteria filling the interior were short, actively 

 motile rods (see footnote on p. 174). 



July II. The following plants were inoculated: Potato (7 plants), tobacco (Connecticut seed leaf, 2 plants), cucumber 

 (4 plants), petunia (2 plants, 6 shoots), Solatium nigrum (i plant), 

 Datura stramonium (2 plants), Datura tatula (?) (i plant), Physalis 

 crassifolia (i plant, several shoots). Twenty-five inoculations were 

 made by needle-pricks on a very hot, sunny day. The inoculated 

 parts were shaded. The cultures used were tubes of beef-broth Nos. 

 i, 2, 3, 4, 5, 6, and 8 of July 8, from sugared peptone-water in fer- 

 mentation-tubes (descended from egg-plant from Charleston, S. C.). 

 The potatoes were tall shoots, half-grown in 8-inch pots, and each plant 

 was inoculated from a separate tube (about 30 pricks in all) . Numerous 

 check-plants were held. The tobacco was inoculated (100 pricks) in 

 a big leaf. The 

 Datura tatula (?) 

 was a young, 

 vigorous plant. 

 The plants of D. 

 stramonium were 

 old and stunted. 



Result. Very successful 

 on potato (Bull. 

 12, pi. I, fig. 8), 

 Solatium nigrum, 

 Physalis crassi- 

 folia, and Datura 

 stramoniu m . 

 Feeble infection 

 in petunia. The 

 inoculation on 

 D. tatula failed. 

 There was pos- 

 sibly some local 

 disease on one 

 of the tobaccos. 

 Saved in alcohol. 

 All the potato 

 plants con- 

 tracted the dis- 

 ease. The first 

 signs were ob- 

 served on the 

 third day, and 

 on the sixth day 

 there was de- 

 cided wilt of the 

 leaves. The 

 weather was 

 very hot. Ex- 

 amined micro- 

 scopically, the 

 stems of 5. 

 nigrum swarmed 

 (figs. 89, 90, 91, 

 92) with small to 

 medium-sized short rods, single or in pairs, with a constriction; a tremulous motion. 



July 23, 24, 25, 27. Potato plants (4, each with several shoots) were used for this experiment. The inoculations were 

 made by potato-beetles which were fed for some hours on tips of potato-vines badly wilted and blackened by 

 Bact. solanacearum (inoculations of July 1 1), then colonized on the sound vines for some hours. 



*FiG. 90. Cross-section of small portion of stem of black nightshade, showing Bacterium solanacearum in vessels 

 and connective tissue. This figure is a detail from one of the bundles shown in fig. 89 introduced to give an idea of 

 the size and shape of the bacteria. The bacterial masses are somewhat contracted from the walls of the vessels owing 

 to the use of strong alcohol as a fixative. The cells marked X belong to a medullary ray. Slide 1 19(14. 



fFlG. 91. Longitudinal radial section of a portion of the vascular ring of the stem of Solanum nigrum, showing 

 location of the bacteria. The right-hand side faces the inner phloem. A cavity is visible in the bundle. Plant inocu- 

 lated with Bacterium solanacearum by needle-pricks on July n, 1896; stem fixed in strong alcohol July 24. A detail 

 from another section in the same series is shown in fig. 92. The entire stem in cross-section is shown in fig. 89. Drawn 

 with the help of the Abbe camera, 16 mm. objective and 12 ocular. From slide 1 19(9. 



Fig. 90.* 



Fig. 91. f 



