78 



required at this température, and this kirger amount being 

 formed only slowly during the stay at this température. 



The results of Czapek, represented by a descending 

 line, which from 15° C. to 30° C. runs horizontally, also 

 give rise to the supposition, that hère a limiting factor 

 came into phiy. 



A second point, where the curve probably does net 

 accurately represent the relation between température and 

 presentation-time, is at 0° C, at which température the 

 presentation-time suddenly becomes extraordinary long. 

 The température-coefficient between 15° C. and 5° C. is 2.6, 

 between 5° C. and 0° C. it is 20.3 (cf. p. 67). I think it 

 very probable that the cause of this phenomenon must 

 be sought in tho fact that at this température growth is 

 nearly at a standstill. If the sudden rise in the presenta- 

 tion-time is really dépendent on this fact, we hâve hère 

 another instance of a secondary influence and might 

 range this under the limiting factors in Blackman's 

 sensé. Our knowledge of this subject is, however, not 

 sufficient, to say anything positively. The lack of an 

 exhaustive investigation of the relation between température 

 and growth makes itself felt hère. 



§ 15. The investigation of van I ter son and 

 Miss van Amstel. 



So far this investigation is the only one in which the 

 authors hâve opposed Blackman's theory. We must 

 therefore consider more fully, whether the results obtained 

 there really justify the conclusion that Blackman's 

 theory must be rejected. ') 



1) I give a vcrv short summary onlj- : fur ail détails the original 

 paper must be consulled. 



