DIFFUSE CHEMICAL ACTIONS 



341 



Paraffin 



kept in darkness, the streaming ceased in two or three days. This is, 

 however, simply because of the accumulation of the injurious products 

 of respiration, for Kiihne and Ritter 1 found that streaming might continue 

 for as long as nineteen days in the absence of oxygen, and by the aid of 

 the apparatus shown in Fig. 59, which was sealed and kept under water, 

 Ewart 2 was able to demonstrate the continuance of streaming in darkness, 

 and in the absence of oxygen, for from six to eight weeks. This applies to 

 Char a foetida, Nitella translucent, and N. flexilis, other species being less 

 pronounced facultative anaerobes. In general, Clark found that streaming 

 recommenced in aerobic plants under a pressure of from i to 7 mm. of 

 oxygen, which is below the pressure required for normal aerobic respiration. 

 The contradictory results of certain observers are partly due to the 

 presence of oxygen or of poisonous impurities in the hydrogen employed, and 

 partly to individual and cultural differ- 

 ences in the material used. Lopriore 3 

 stated that streaming never ceased in 

 hairs of Tradescantia and of Ciicurbita 

 either in hydrogen or carbon dioxide, 

 but this was undoubtedly due to the 

 presence of oxygen in the gases used 4 . 

 Lopriore 5 obtained different results in 

 the morning to those yielded in the 

 evening, possibly owing to changes of 

 tone, and Josing G found that etheriza- 

 tion causes streaming to cease sooner 

 in the absence of oxygen. Carbon 

 dioxide in all cases ultimately acts 

 injuriously 7 , but cuticularized hairs 

 which seem to be naturally accommo- 

 dated to high internal percentages of 

 carbon dioxide may continue to show streaming in a mixture of 80 per cent, 

 carbon dioxide and 20 per cent, oxygen. As in other cases, a temporary 

 shock-stoppage may be produced by the sudden change from air to carbon 

 dioxide 8 . In no case, except in the very doubtful one of Pelomyxa, does 

 pure hydrogen exercise any direct injurious action, apart from that due to 

 its displacing the oxygen required for respiration. The same applies to 

 nitrogen and carbon monoxide in the case of plants, and as regards 



Mercury 

 Valve 



Alk'Pyrooallol 



FIG. 59. Apparatus for testing the anaerobism of 

 Chara and Nitella (two-thirds natural size). 



1 Kiihne, Zeitschr. f. Biol., 1898, N. F., Bd. xvm, p. 30; Ritter, 1. c., p. 351. 



2 Protoplasmic Streaming in Plants, 1903, p. 42. 



3 Lopriore, 1. c., 1895, p. 28. * Samassa, 1. c., p. 2 ; Ewart, 1. c., p. 38. 

 5 Lopriore, 1. c., 1902, p. 118. 6 Josing, 1. c., p. 221. 



7 Cf. Samassa, 1. c., p. 2 ; Klemm, 1. c., p. 36 ; Kiihne, 1. c., 1864, p. 106 ; Ewart, 1. c., p. 78. 



8 Cf. Ewart, 1. c., p. 79. 



