•13- 



each represented by seven cultixt'es. Each sot of seven 



like cultures was distributed throughout the seven 



Sinp-le 

 different temperatures tested, so that a/series comprised 



twenty-one cultures for each temperature. All of the twenty- 

 one nt;trient solutions of any one solution type v/ere thus 

 simultaneously tested for each/the seven temperatures, and 

 each culture series comprised 147 cultures. The completed 

 study involved all six types, or 882 cultures. Each 

 of the six series, excepting those for the lov/est tempera- 

 ture; , was repeated once^so that 1638 tests were made. 

 The nuitrient solutions were all renewed after each 24- 

 hour period, for four renewals, the cultures being 

 discontinued on the fifth day. 



The temperature controls used were those of the 

 battery of chambers for temperature control at the 

 Laboratory of Plant Physiology of the Johns Hopkins 



University, v/hich has been described in its essentials 



(5) 

 by Livingston and Pavfcett . The seven different 



temperatvcres employed in these tests were as follows: 



35°, 31°, 28°, 25°, 21°, 17°, and 13° G. Variations from 



these values vieve never as great as one degree. No 



^ ^■'Livings ton, B.E. and H. S. Fav/pett* A battery 

 of chambers with different automatically maintained tempera- 

 tures. Phytopathology 10:356-340, 192Q. 



