108 



C>i>Ti>n>r Temi-khatihk ii>k (iRowni. 



No special experiments have been instituted to determine at what 

 temperature growth of ]%. hyacinth! is most I'apid. })ut from a careful 

 collation of the records of several hundred cultures made during- the 

 past four years and kept at room temperatures — i. e., of all cultures 

 which were examined frequently enough during the first few days of 

 growth, and for which the necessar}'^ temperature records were set 

 down — I find that, on good media, growth was slow at lO*^ 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 3'ear, and some- 

 times for several days together the room temperature would be nearl}^ 

 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 ma}^ be placed at 28° to 30° C. 



Minimum TKMPEKATtTRE fok Growth. 



On very favorable media this is believed to be about 4° C. for Ps. 

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

 sugar beet cylinder inoculated copiously with bright yellow slime from 

 a starch jelly culture 8 days old and kept in the ice chest at 1()° to 

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

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

 removed to room temperatures. Five da3^s afterwards there was a dis- 

 tinct yellow growth coA^ering more than 2 square centiiuetei-s of the 

 surface. 



(2) A tube of unneutralized 1:2 beef broth (stock 204), inoculated 

 with a large loop from a well-clouded beef broth culture 7 days old 

 and put into the ice chest at 10° to 12° C, was clouded verv feebly at 

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

 67 hours. 



(3) Two freshly prepared cjdinders of coconut, standing in test 

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

 approximatel}^ 1 c. mm. of 3'ellow slime from a coconut culture 4 days 

 old. These tubes were put into the ice chest. In 42 hours there was 

 a slight but distinct growth in each tube, the tempcnniture, 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 off 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 54 hours), there was a slight growth in each tube, although 

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



