72 



of Ps. camjpestris. Ps. phaseoli has not been tested so extensivelj^ but 

 reacts in the same way, so far as tried, i. e. , it produces no gas and is 

 strongl}^ aerobic. Ps. stewarti produces no gas and appears to be 

 strictly aerobic, but is able to get along w^th a relatively' small amount 

 of air. A small amount of some non-volatile acid or acids appear to be 

 produced by it from grape sugar, cane sugar, galactose, and mannitol, 

 but not from glycerol. 



Growth in Nitrogen. 



The tests were made in U tubes holding 250 c. c. and open at each end. 

 Two verv short cotton-plugged test tubes containing the freshly steamed 

 culture medium were inoculated with Ps. hyacinthi and thrust, one 

 above the other, into one arm of the U tube, which was then tightly 

 closed with a soft rubber stopper and plunged, for greater security, 

 into a beaker of glycerin. Into the other arm was thrust quickly a 

 longer test tube filled with a mixture of pyi'ogallic acid, caustic pot- 

 ash, and water. This end of the tube was then plunged into a beaker 

 of mercury and held down until the absorption of oxj^gen equalized 

 the pressure and enabled it to remain down of its own weight — a period 

 of some hours. The following experiments were tried in these tubes: 



(1) The first experiment was with cylinders of freshly prepared 

 coconut, a medium on which this organism was known to grow with- 

 out retardation. Four tubes were inoculated. Two received each one 

 loop of yellow slime from a solid culture T days old, which slime 

 was rubbed carefully over the whole surface. Two received each two 

 loops of fluid from the bottom of a potato (?) culture 7 da3''s old, 

 after shaking. One tube of each set was held as a check. The other 

 2 tubes were put into one arm of a U tube the other end of which 

 received a tube holding 2 grams of pyrogallic acid and 25 c. c. of 13 

 per cent caustic potash water. The room temperature during the 

 experiment ranged from 17° to 26° C. The oxygen was gradually 

 absorbed and the tubes remained exposed to the nitrogen for 15 days. 



Result. — In 48 hours from the time of inoculation the check tubes 

 showed a good growth. On the eighth day the check cylinders were 

 covered with an abundant, smooth, wet-shining, canary-yellow growth. 

 In each tube there was at least 6 sq. cm. of this growth. During the 

 same time, in the tubes exposed to the nitrogen, there was no visible 

 growth. 



On the fifteenth day the mercury seal was broken and the tubes 

 were taken out and examined more criticall}". One tube showed no 

 growth whatever and the other an extremely slight pale-3'ellow 

 growth, best seen with a hand lens, and aggregating not over one- 

 fourth of 1 sq. mm., 1. e., not more than might have grown around one 

 of the coarser fragments of the inserted slime before all of the oxygen 

 was absorbed. At this time the contrast with the checks was very 



