56 



BACTERIA IN RELATION TO PLANT DISEASES. 



They give a decidedly alkaline reaction to moist litmus paper and are not noticeably viscid 

 (fourteenth day). On opening plates of this age they had a peculiar smell common to many 

 bacteria (trimethylamin ?). The buried colonies are elliptical-pointed or spindle-shaped, 

 and small. 



On slant peptonized beef-agar the organism makes a thin, rather scanty, wet-shining, 

 pale yellowish growth which is sometimes scarcely distinguishable from the agar itself. In 

 some streaks 5 days old the penholder was visible through three superposed tubes. The 

 streak is finely granular under the hand-lens. A small amount of pale yellow precipitate 

 forms in the fluid in the V and numerous prismatic crystals are sometimes present in the 

 agar; 200 or more of these crystals were observed in a single tube. 



In beef-agar stab-cultures there was a variable growth in the stab, often fairly good the 

 whole length, but always thinning out below and sometimes scanty. There was a good, 

 wet-shining, pale yellow surface growth. In one set of tubes inoculated from slant agar and 

 described the third day, the nail-head was 4 to 5 mm. in diameter, wet-shining, and maize 

 yellow. The slime of very old cultures may be buff-yellow. The agar is not stained. 



Fig. 29. 



Fig. 30. f 



On agar with cane-sugar or fruit-sugar there is slow growth at 30 C. or under (RGS.). 



Greig Smith describes the streak on slant glycerin agar as "a thin, broad, translucent 

 white, moist, glistening growth, with turbid condensed water. The color deepens to a prim- 

 rose-yellow. " 



On agar containing 10 per cent saccharose and 0.1 per cent peptone there is a thin, white 

 fluid growth, which gravitates into the condensed water, in which there is a yellow sediment 

 (RGS.). 



A very good medium is a solution of 4 per cent agar added to an equal amount of neu- 

 tralized cane-juice containing 0.5 per cent peptone. With a greater per cent of peptone 

 there is better growth at first, but ultimately less (RGS.). 



The writer obtained a very copious growth on slant tubes of sugar-beet agar, as much 

 growth as on cane-juice agar. This medium was made as follows : Juice of sugar-beets 300, 



*Fig. 29. Flagella of Bacterium vascularum stained by Lowit's method. Selected samples from a cover-glass 

 preparation (young agar culture in sterile water). Slide B, mordanted one-half minute, stained 5 minutes, Jan. 9, 1906. 



tFiG. 30. Rods of Bacterium vascularum from a young agar culture stained by Lowit's method. Mordanted 0.75 

 minute, stained 2 minutes. A few flagella show feebly in some places. Slide A, January 9, 1906. 



