90 AERATION AND AIR-CONTENT. 



tatively anaerobic. He was unable to find either growth or tro- 

 pistic movement under the total exclusion of oxygen. 



Samassa (1900 : 320) confirmed Lopriore's observation that pure 

 oxygen did not increase the rate of protoplasmic movement in the 

 stamen-hairs of Tradescantia. The lack of oxygen stopped the 

 movement quickly, and in nitrous oxid it ceased in 15 to 20 minutes. 

 In agreement with Lopriore, he found an adaptation to carbon dioxid, 

 when successive mixtures were employed with more CO2 and less 

 oxygen, but in all cases pure carbon dioxid caused the motion to 

 cease. The action of CO2 was considered to be that of an acid, since 

 the normal resting nucleus assumed the same foamy appearance 

 noted in dilute solutions of sulphuric, acetic, and formic acids. The 

 conclusion was reached that the cessation of motion due to the with- 

 drawal of oxygen also stops mitosis, contrary to the observations of 

 Demoor. 



Pfeffer (1900 : 546) called in question Kiihne's assumption that 

 the streaming of the protoplasm of Nitella for 50 days in darkness 

 was due to traces of oxygen in the protoplasm, and thought the 

 proper explanation to be that Nitella is a partial anaerobe. He 

 regarded the whole matter as demanding more study, since Ewart 

 has shown that a minute trace of oxygen is sufficient to maintain 

 movement in Chara almost indefinitely. 



SabUne (1903 : 488) found a considerable number of mitotic fig- 

 ures in root-tips of Vicia faba deprived of oxygen for a period of 2 

 hours. The figures were more or less modified, chiefly by the absence 

 of the formation of a cell-plate and the faintness of the spindle. 



O. Nabokich (1904 : 62) subjected young seedlings of Helianthus 

 annuus, Pisum sativum, and Phaseolus vulgaris to an oxygenless 

 atmosphere for 5 to 51 hours. Her chief conclusion was that a 

 normal anaerobic mitosis occurs with some higher plants. In the 

 young leaves and growing-points of sunflower all mitotic stages were 

 found in the cultures for 5, 18, 23, 30, and 43 hours, while with 50 

 hours no figures were seen. The buds of pea and bean behaved 

 similarly, though mitotic figures disappeared earlier. Pea roots 

 were much more sensitive, the figures disappearing after 20 hours, 

 while in root-tips of the bean practically none were found after 5 

 hours. In nearly all cases the cell- wall was formed normally in Heli- 

 anthus, but it was suppressed after 5 hours in Phaseolus. The author 

 concluded that cell-division is independent of the presence of oxygen, 

 and that the injury observed was due to secondary influences. 



Andrews (1912 : 473) found that hydrogen stopped protoplasmic 

 movement in Mucor mucedo and M. stolonifer in 20 minutes in moist 

 air, while Schroter found 5 minutes sufficient. In dry air it required 

 54 minutes for hydrogen to stop the movement. In this case, 5 

 minutes were required for streaming to begin again instead of 1 

 minute after moist air. 



