Micro-organisms of" Maple Sap 



585 



number of tests were made in an effort to fix the exact death 

 point accurately, but the experiments indicate clearly that the 

 death point of these organisms under the conditions" employed, 

 is not constant within at least 0.5 ° C. The final conclusions are 

 recorded in the table below : 



Optimum temperature. — -The best growth with all strains oc- 

 curred at approximately 25 ° C. 



Maximum temperature. — At 36.7 to 35 ° C. only Ps. fluores- 

 cens and Ps. putrida developed in 24 hours. At 33.4 to 30.8 

 in the same length of time Ps. alba. Ps. fluorescens. Pr. longa, 

 Ps. mesenterica, Ps. putrida, CXII, and CXL, showed growth. 

 At 31.2 to 28.5 Ps. albo, Ps. fluorescens, Ps. longa, Ps. mesen- 

 terica, Ps. tenuis, Ps. putrida, CXII. CXL, and LI developed. 

 The experiments indicated that all strains could grow at tem- 

 peratures up to 33 C. Only I's. fluorescens, Ps. putrida, and 

 CXV developed at 36 C. in 7 days. In no case was the growth 

 at these higher temperatures as good as it was below 30 C. 



9. Drying. — Small cover slips were placed on bits of pa- 

 per in petri dishes and sterilized in the oven. Each was then 

 inoculated with one loop of young broth culture, the age of 

 which varied in the different experiments from 1 to 3 days. They 

 were allowed to remain in the dark at room temperature. At 

 intervals, cover slips were removed and dropped into tubes of 



