310 



BACTERIOLOGY. 



some of them a bright-green color that is most conspic- 

 uous where it is in contact with the air. This green 

 color, which becomes more and more marked as growth 

 advances, is not seen in the growth itself to any extent, 

 but is diffused through the medium on which the organ- 

 ism is developing. Ultimately this color becomes much 

 darker, and in very old agar-agar cultures may become 

 almost black (sometimes very dark-blue green, at others 

 brownish-black). 



FIG. 58. 



Colony of ps. aeruginosa after twenty-four hours 

 on gelatin at 20-22 C. 



FIG. 60. 





Colony of ps. smiginosa after forty-two hours on 

 gelatin at 20-22 C. 



. To a fresh agar culture of this organism, in 

 which the green coloration of the medium is especially 

 marked, add about 2 c.c. of chloroform. Shake gently, and 



Stab-cnlture of 

 ps. aeruginosa in gel- 

 atin after twenty- 

 eight hours at 22 C. 



