108 



OPTi>rr>[ Temperature for Grcoth. 



No special experiments haA'e been instituted to determine at ^^hat 

 temperature growth of JPs. hyacinthi is most rapid, but from a careful 

 collation of the records of several hundred cultures made during the 

 past four 3^ears and kept at room temperatures — i. e., of all cultures 

 which were exaniined frequently enough during the first few days of 

 growth, and for which the necessary temperature records were set 

 down — I find that, on good media, growth was slow at 10° to 12° C, 

 moderate at 18° to 25° C. , and fast (for this organism) at 28° to 30° C. 

 These cultures were instituted at all seasons of the year, and some- 

 times for several days together the room temperature would be nearly 

 stationary — e. g., at 18°, 25°, or 30° C. In a few instances I have thus 

 been able to compare at difterent temperatures the rate of growth 

 when the inoculations were made with the same amount of material 

 taken from cultures of the same age and kind 



Using these records, therefore, as a basis for judgment, the opti- 

 mum temperature for growth may be placed at 28° to 30° C. 



]\IiNiMUM Temperature for Gr<^wth. 



On very favorable media this is believed to be about -1° G. for Ps. 

 hyaclnthL Only four sets of experiments have been made. (1) On a 

 sugar beet cylinder inoculated copiously with bright yellow slime from 

 a starch jelh^ culture 8 days old and kept in the ice chest at 10° to 

 12° C. (temperature possibl}^ at times as low as 7° or 8° C. , but never 

 lower) no visible growth appeared in 12 days. The tube was no\v 

 removed to room temperatures. Five days afterwards there was a dis- 

 tinct 3^ellow growth covering more than 2 square centimeters of the 

 surface. 



(2) A tube of unneutralized 1:2 beef broth (stock 201), inoculated 

 with a large loop from a well-clouded beef broth culture T day old 

 and put into the ice chest at 10° to 12° C, was clouded ver}^ feebiV at 

 the close of the fifth day. A check tube at 21° C. clouded feebly in 

 67 hours. 



(3) Two freshly prepared c^'linders of coconut, standing in test 

 tubes in an abundance of distilled water, were each inoculated with 

 approximately 1 c. mm. of A^ellow slime from a coconut culture 4: days 

 old. These tubes were put into the ice chest. In 12 hours there was 

 a slight but distinct growth in each tube, the temperature, however, 

 had been higher than was anticipated — i. e., 10° to 15° C. These tubes 

 were now shaken for 10 minutes — i. e., until all trace of the yellow 

 growth was washed ofi' and dissolved in the fluid. They were then 

 put back into the chest with a larger quantity of ice. On June 2, 4 

 p. m. (after 51 hours), there was a slight growth in each tube, although 

 the temperature had remained under 8° C. On June 3, 9 a. m. (tern- 



