6o 



BACTERIA IN RELATION TO PLANT DISEASES. 



Greig Smith states that there is very slow liquefaction both of cane-gelatin and ordinary 

 gelatin. This is seen usually only as a slight depression of the medium under the streak. 



On ordinary gelatin, according to Greig Smith, the growth is scanty and ivory white in 

 color. By this he means, perhaps, the pale yellow of old ivory. The organism I have 

 studied is not pure white on any medium, although for the first few days it might be thought 

 to be so. In streak-cultures the slime slowly gravitates to form a yellowish-white mass at 

 the bottom of the slant (RGS.). On glucose-gelatin the growth is less luxuriant and less 

 deeply colored than on cane-gelatin (RGS.). 



There was a striking difference in the amount of growth on steamed cylinders of Com- 

 mon Green cane and that made on Striped Green, Common Purple, and Striped Purple cane. 

 On the first-named variety there was at least 50 times as much growth as on the others. On 

 the last three there was little growth, while on the other growth was good though not copious. 

 Greig Smith obtained no growth on slices of cane (variety Rappoe ?) inocu- 

 lated with Bact. vascularum. The organism makes a much better growth on 



potato-cylinders and on coconut-cylinders. 

 The growth on potato is generally better 

 than on agar (see pi. 1 1, fig. 13). It is moder- 

 ately abundant, i. e., about like that of Bact. 

 hyacinthi, but with rather more slime in the 

 water (fig. 36) ; surface growth smooth, wet- 

 shining, and yellow (between Ridgway's 

 canary yellow and lemon yellow), occasion- 

 ally it is Naples yellow or between lemon 

 yellow and gamboge yellow (3 days). The 

 palest yellow (4 days) was between primrose 

 yellow and straw yellow. Growth is some- 

 times raised and restricted, sometimes flat 

 and watery, spreading over the surface 

 (RGS.). Growth on potato is good rather 

 than copious, and ceases early, indicating 

 that the organism has only a small ability to 

 obtain its food from the potato-starch. Re- 

 peated tests showed much starch present, 

 even in old cultures. Mashed cylinders became deep bluish-purple or wine-purple in iodine 

 water. The undisturbed surface layer became dirty purple or brown-red. The growth 

 is [mostly out of the water. There is no such rapid destruction of starch and piling up 

 of the bacteria in the water as occurs in cultures of Bacterium campestre. 



The slime is distinctly yellow on all potatoes, but bright yellow on some and paler on 

 others. The potato is moderately grayed, but mostly out of the water. Old cultures (43 

 days) were alkaline to litmus. Young cultures are also alkaline. 



On beet-cylinders (acid medium) there is only a small amount of growth, but on steamed 

 onion-bulbs and cauliflower-cylinders there is a good growth of the organism. 



On carrot and turnip there is a raised, slimy, yellow growth, at first restricted, but 

 eventually covering the surface and gravitating (RGS.). 



There is a good yellow growth on coconut-cylinders which remain unstained. 

 Bacterium vascularum makes a good, though not copious, growth in +15 peptonized 

 beef- bouillon. There is moderate clouding of the fluid, beginning usually within 24 to 48 

 hours, and when the tube is shaken there are distinct rolling clouds. Sometimes the cloud- 



Fig. 35.* 



Fiji. 36.f 



TIG. 35. Tear-drop formation of Bacterium vascularum on cane-juice gelatin. After R. Greig Smith. 



fFic. 36. Streak-cultures of Bacterium vascularum on potato cylinders (the lower part in water) after 8 days at 

 room-temperature. Potato grayed out of the water. The darkest part is the wet-shining yellow slime. Each tube 

 inoculated from a single poured-plate colony. 



