85 



(d) Coconut. — March 20, no growth. March 21, extremely thin (barely visible) 

 bnff-vellow growth over 3 sq. cm. March 23, a thin, pale, buff-yellow growth now 

 covers al)Out 5 sq. cm. March 27, a rather scant buff-yellow growth over 8 sq. cm. 

 No retardation. 



B. amylovorus- 



(a) Affcir. — March 20, no growth. March 21, a distinct growth on the lower end 

 of the slant. March 23, the white growth slowly increases. 



This closes m}" studies of the aerobism of Ps. hyacinthi and related 

 species. All the various experiments lead to substantially the same 

 conclusions: (1) Px. hyacinth! and the other yellow species of Pseudo- 

 monas are more strictly aerobic than most species of bacteria; (2) while 

 somewhat variable among themselves none of these yellow-plant para- 

 sites will survive exclusion of oxygen for more than a very few weeks; 

 (3) nitrogen, hydrogen, and carbon dioxide seem to be only negatively 

 harmful; (-1) the organisms were more tolerant of these gases on some 

 media than in others. They were especially susceptible in beef broth, 

 in peptone water, and on agar. 



RELATIVE NUTRIENT VALUE OF CARBON COMPOUNDS. 

 Bouillon and Peptone Water with Various Sugars, etc. 



The few results obtained may be summed up as follows: 



(1) A feeble clouding was obtained with Ps. hyacwthi in a fluid con- 

 sisting of 1 part of strongly alkaline beef broth (286b) in 500 parts of 

 distilled water. Ps. campestrls and Ps. 2>haseoll also clouded this fluid. 

 These cultures were made in clean tubes of resistant glass. 



(2) Ps. hyacinthi grew readily in distilled water containing 1 to 2 

 per cent of Witte's peptonum siccum, and the precipitate was yellow. 

 Growth in I per cent peptone water in the open end of fermentation 

 tubes, as we have already seen, was increased by the addition of 1 per 

 cent doses of grape sugar, fruit sugar, cane sugar, or dextrin, and 

 was not perceptibly increased by the addition of 1 per cent doses 

 of milk sugar, maltose, mannitol, or glycerol. If under these condi- 

 tions any acid was formed from any of these substances^ it was over- 

 looked or obscured by the alkali. 



(3) In distilled water (10 c. c. portions in tubes of resistant glass) 

 containing -1 per cent of Witte's peptonum siccum and 4 per cent of 

 dextrin there was little or no retardation of growth. On the tAvelfth 

 day the fluid was plainly alkaline to litmus. On the twenty-ninth 

 day there was an a])undant yellow rim and a very copious dull-yellow 

 precipitate (<> nnn. deep). The cloudy fluid was plainly and rather 

 strongly alkaline. On this date there was several times as much pre- 

 cipitate as in the corresponding tubes of Ps. carnpestris and Ps. plmstikli. 

 On the fortieth day the fluid was strongly alkaline. It was still cloudy 

 with rolling clouds on shaking, and thcrc^ was no brown stain in it. 

 On the sixty -fifth day the fluid was moderatel}' alkaline. No crystals 



