THE INFLUENCE OF FREE OXYGEN UPON STREAMING 41 



investigations of this kind, and of the importance of securing absolute 

 purity in the gases employed, it may be mentioned that Lopriore 1 came 

 to the conclusion that streaming cannot be stopped in cells of Tradescantia 

 by pure hydrogen, while Demoor 2 has stated that streaming continues in 

 nitrous oxide (N 2 O) and is even accelerated. Samassa 3 has, however, shown 

 that the latter statement is erroneous, and my own observations, as well as 

 those of Kuhne 4 and Demoor (1. c., p. 33), conclusively prove that in an 

 atmosphere of pure hydrogen streaming ceases in non-illuminated hairs of 

 Tradescantia within from fifteen minutes to two or three hours, according 

 to the temperature, and also the age and condition of the cells. The con- 

 tradictory results with regard to the influence of pure oxygen are due to 

 the fact that it retards streaming in facultative anaerobes, and temporarily 

 accelerates it in strongly aerobic ones only when previously slow, the 



accelerating influence being 

 especially marked in non-assi- 

 milating cells with cuticularized 

 walls. 



In the case of Chara and 

 Nitella,tiiQ problem is to remove 

 every trace of free oxygen with 

 as little disturbance as possible, 

 and to prevent 

 any injurious 

 accumulation of 

 the products of 

 intramolecular 

 respiration. This 

 can be done by 

 placingahealthy 



FlG. 6. Apparatus for obtaining pure hydrogen and pure CO* free from all oxygen (one-tenth natural size). 



filament of Chara or Nitella in an open tube containing cold boiled 



1 Jahrb. f. wiss. Bot., 1895, Bd. xxvm, p. 531. 



2 Archives d. Biologic I., 1894, xin, p. 163. 



* Unters. iiber das Protoplasma, &c., 1864, p. 105. 



3 Bot. Ztg., 1898, p. 344. 



