méthode" Hans Kniep^) pointed out that the gaseous 

 exchange of assimilating shoots of Helodea canadensis is 

 a comphcated process, especially caused by the différence 

 between the rate of diffusion of carbondioxyde, oxygen 

 and nitrogen. Even the velocities of the dissolving and 

 escaping of thèse gasses into and from the Hquid and from 

 and into the intercellulars (invasion and évasion) seem 

 to play a part. 



In our experiments the circumstances are much more 

 simple than in K n i e p's, because no gasbubbles are 

 evading from the eut ends of the Helodea-shoots in 

 the water which is free of oxygen and streaming 

 along thèse shoots. So the oxygen will come into the 

 water only by diffusion. Moreover we had no nitrogen 

 in our gasmixture. Yet it will be obvious that probably 

 in our experiments the processes pointed out by K n i e p 

 also took place. It will even be proved that the résulta 

 obtained, hâve presumably been determined by similar 

 processes. 



Thus the experiments, which are to be discussed hère, 

 will lead to the conclusion that in fact we did not measure 

 the influence of température on the CO^-assimilation itself, 

 but that physical processes hâve exerted their limiting 

 influence. In spite of this circumstance we are publishing 

 our results now, because they may indicate to others the 

 probable way to obtain the desired results. 



§ 1. The apparatus. 



À side-view of the apparatus used for the experiments 

 is schematically represented in Fig. 1 ; Fig. 2 schematically 

 represents a view from the upperside. 



The cylindrical glassvessel A (35 c.M. long and 2.5 c.M. 

 in diameter) is used for holding the Helodea-shoots. The 



1) Jah 0. f. Wiss. Bot. 56 PfefFerband. 1915, S. 460. 



