doubling of the activity of vital processes by a rise of 

 10° C." 



Although the autiior is evidently convinced that his 

 theory will hâve to apply over the whole field of plant 

 physiology, there are nevertheless processes to which he 

 has not yet been able to extend his conclusions, at least 

 he says at the end of his second paper. „Finally, superposed 

 upon ail this cornes the first category of phenomena that 

 we are content still to regard as stimulatory. — From 

 our présent point of view vision does not extend to the 

 misty conceptions of stimulation upon our horizon." 



In this investigation an attempt will be made to apply 

 the ideas developed by Blackman to the field of pure 

 physiology of stimulus and to test their gênerai validity 

 by the facts. 



The next publication, in which the author shares 

 B 1 a c k m a n's views, was a paper by J. K u y p e r, 

 which appeared ip 1909, and dealt with the influence of 

 température on respiration. ') 



According to the conclusions of this investigation the 

 conception of Blackman is partly applicable to respiration. 



Up to 10° C. the same quantity of GO2 is expired in 

 successive hours and from 10° C. to 20° C. there is a slight 

 increase during successive hours, then follows a period 

 in which the production of CO2 oscillâtes, while above 

 40° C. a regular decrease takes place which represented 

 graphically gives an almost logarithmic curve. Van 

 't H f fs law holds good for Pisum and Triticum from 

 0° C— 20° C. for Lupinus up to 25° C. ; the coefficient 

 for a rise of température of 10° C. lies between 2 and 3. 



1) As Dissertation, Utrecht, 1909 ; in 1910 published in Recueil 

 des Trav. Botan. Néerl., Vol. 7, 1910. The quotations are taken 

 from this last publication. 



