«» AERATION AND AIR-CONTENT. 



Consequently, the question of a short period of anaerobic growth 

 under special conditions has little more than academic value. Even 

 if shown to exist beyond question, it would be without significance 

 for the functioning of organs or the growth of plants. 



PROTOPLASMIC STREAMING AND MITOSIS. 



Corti (1774 : 210) placed Char a in a vacuum under an air-pump 

 and left the plants for 48 hours. The movement of protoplasm in 

 the cells ceased, but began again in 8 to 12 hours after the plants 

 were returned to atmospheric air. On the contrary, Dutrochet 

 (1838 : 31) found that movement continued for 22 days under simi- 

 lar conditions, but Hofmeister (1867 : 49) was able to refute his 

 conclusions by repeating Corti's experiments. Kabsch (1862 : 341) 

 observed that protoplasmic movement in stamen-hairs of Tradescan- 

 tia ceased after 45 minutes in CO2, but in air it returned after 15 to 

 20 minutes. After 24 hours in CO2 the protoplasm became coagu- 

 lated and was no longer capable of response. The assumption was 

 made that the cessation of movement was due to the lack of oxygen 

 rather than to the direct effect of carbon dioxid. Klihne (1864 : 

 88, 104) also showed that there was no protoplasmic movement in 

 the absence of air or in an atmosphere of hydrogen or CO2. This 

 held also for Myxomycetes, which showed no movement and no 

 development in the absence of oxygen. 



Frank (1872) kept shoots of Elodea under oil for several days, and 

 found that movement ceased, to begin again with access of oxygen. 

 Moller (1884) found that nitrogen stopped the movement of proto- 

 plasm in Elodea in 1 to 2 hours when the leaves were placed in the 

 dark, and that the protoplasm finally contracted under longer expo- 

 sure. He concluded that all gases, with the exception of oxygen 

 and air, had an injurious effect, while some of them were actually 

 poisonous. 



In a study of protoplasmic movements in the absence of oxygen, 

 Pfeffer (1887) reached the conclusion that not only movement but 

 photosynthesis also was suppressed in the absence of free oxygen. 

 He found some movement for a time after the withdrawal of oxygen 

 and explained this as a result of minimal amounts which could not 

 be absolutely excluded. 



Clark (1888 : 273) observed that the streaming of the plasmodia 

 of slime-molds ceased in the absence of oxygen in a few minutes, 

 and readily began again upon the access of air. The complete with- 

 drawal of oxygen also stopped the movement in Tria7iia and Urtica, 

 but it was renewed under a pressure of 1.2 mm. and 2.8 mm. respec- 

 tively. In the case of flagellate forms, such as Euglena, the with- 

 drawal of oxygen produced a resting-stage in the zoospores in a few 

 minutes. With Stylonichia, a pressure of 2.5 mm. caused the indi- 

 vidual to come to rest and to flatten out, while an increase of the 



