aid as effective conditions ar« more precisely controlled in 

 experimentation* 



With maintained temperatures progressively either higher 

 or lower than the optimal range these rates of fungus growth are 

 progressively lower. The data given in tahles III - VI show 

 that the rates "become ~ero for each fungus when a certain tem- 

 perature higher than the optimal range is passed, and it is 

 clear from other studies of plant growth rates - that a similar 

 temperature might he found "below which the rates would he zerc. 

 Thus, growtn itself, the rery occurrence of the process, can 

 take place (lor any given fungus and for any given set of non- 

 temperature conditions) only within a certain range of maintain- 

 ed tempe/acjres, this total temperature range being considerably 

 larger than the corresponding optimal range and including the 

 latter within its limits. These two temperature limits have 

 heen called the minimum and maximum temperatures, and they are 

 readily determined, i^ any case, with a certain degree of pre- 

 Cjsion. But, even for these, the precision of statement is 

 not yery great. On the whole, it is beat to consider all 

 thrae of these so-called cardinal points of temperature influ- 

 ence as only approximate in the few cases where attempts have 

 "been made to determine them at all, and the results of the 

 present study must he regarded in this way. 



It is obvious that the data of growth rates -- as those 

 of all other process rates must always involve a duration fac- 

 tor , a process is measured in terms of the amount of woi k 

 accomplished, or of product produced during a given time per- 

 iod. Since the change considered may go forward more or less 

 rapidly during different partial time periods within tne per- 



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