BROWN ROT OF SOLANACEAE. 



195 



day such milk was approximately Ridgway's indigo blue ; after 3 months it was dark hya- 

 cinth blue (pi. 23, fig. 7) ; but the fluid was neither viscid nor gelatinous. Litmus in milk is 

 sometimes a little reduced (white) in the bottom of the tubes. The bacterial precipitate is 

 white. In another set of tubes of litmus milk examined at the end of the seventh week the 

 color was recorded as a clear intensely dark blue. All these milks were cream-free. 



Ljtmus-laetose-agar streaked with this organism becomes slowly a deeper blue. There 

 is never any reddening, but sometimes the litmus is partially reduced and the agar finally 

 browns. The behavior in cream-free litmus milk is like that of the culture figured on pi. 41. 

 The streak of the District of Columbia organism on slant litmus-lactose-agar after 10 days 

 at about 27 C. was white, wet-shining, and there was a copious whitish precipitate in the 

 V; the upper half of the agar was blued very decidedly, in the lower half the litmus was 

 reduced. The surface of the slant beyond the streak was iridescent. The agar was not 

 then browned, but later (seventh 



week) it was browned decidedly 

 and the surface growth was a dirty 

 brownish-white ; the extreme upper 

 part of the agar continued bluer 

 than the check-tube, but in the 

 lower part the formation of the 

 alkali was masked by the brown 

 stain and the reduction processes. 



The organism does not liquefy 

 gelatin (experiments of 1895-96, 

 repeated in 1904 and in 1905), at 

 least not when made as described 

 in vol. I of this monograph. The 

 surface colonies in gelatin are small, 

 circular, thin, thin-edged, smooth, 

 white, wet-shining; the buried col- 

 onies are globose, yellowish or 

 brownish, and smooth, with well- 

 defined margins. In stab-cultures 

 (fig. 111) the upper part is best de- 

 veloped, but growth was not rapid 

 at 24 C. and ceased at io C. The 

 Virginia organism grown in gelatin- 

 stabs for 7 days at 22 to 25 C, and then 2 days at 15 C, developed a thin, white, wet- 

 shining surface growth which was roundish and about 3 to 4 mm. in diameter. Growth 

 was visible the whole length of the stab, but was best at the top. There was no stain, no 

 gas, no liquefaction, no development of crystals. The District of Columbia organism grown 

 for 10 days in gelatin-stabs at 25 C. was similar in all respects to the above. The + 10 

 gelatin in old cultures becomes dusky or browned, especially in the upper part of the stab. 



In agar the buried colonies remained small and were irregularly round or oblong, with a 

 roughened margin. The surface growth was white or gray-white at first, then brownish. 

 The general form of the surface colonies after some days on +15 nutrient agar at 25 C. is 

 shown in figs. 112, 113. As a rule the agar was stained brown by growing this organism 

 on it (pi. 23, fig. 2, and pi. 41, fig. 8, from tobacco, will answer for potato and tomato). 



In thin sowings on peptonized beef agar the organism from the South Carolina tomato, 

 used for successful inoculations in 1901, formed colonies about 2 to 3 mm. in diameter at the 



Fig. 104/ 



*Fig. 104. Cross-section of a few cells of a potato tuber rotted by Bacterium solanacearum. Plant No. 14, 1S96, 

 inoculated June 15. A detail from fig. 82 made under x, showing cells occupied by the bacteria. The starch-grains 

 which lie buried in the bacterial mass appear to be uncorroded; they polarize, but I was unable to detect any rings of 

 light and dark substance in them. Section stained with carbol-fuchsin. Drawn with the Abbe camera. Slide 156(2. 



