28 



})osiii-(' to (lilTeri'iil (Icgi'ct's ol" alinosphcric nioislurL' (rela- 

 ti\(' liuniidily 25% to 100%). Pleurococcus was found to 

 witlistaiul -80° for at least 24 to 26 hours, irrespective of 

 the humidity to which it had previously been subjected. 

 SficJiococcus and Apafococcus proved themselves less re- 

 sistant ; they were killed at - 80° in 1 wo hours and one hour 

 respectively. However, with the relative humidity re- 

 duced to 50% they were equally as resistant as Pleuro- 

 coccus to a temperature of -80°. 



AVarl)iiri; (l!*!!)) maintained in li(|ui(l air for one hour 

 suspensions of ChlorcUa in Knopp's solution. The cells 

 sustained no injury from the treatment. The chlorophyll 

 granules were unaltered while they became enlarged and 

 showed structural changes in Euglena treated in a similar 

 manner {Bioch. Ztschr., 100, 234). 



Kiircher (1931) exposed Stichococcus hacillayis, cul- 

 tured on agar slants in test tubes, to - 70° for 1 to 8 days, 

 or to - 183° to - 192° for 13 hours. The algae were not 

 killed. 



Becquerel (1932d and 1936) found that Profococcus and 

 Pleurococcus grew normally after having been subjected 

 in the dry state to the lowest available temperatures. The 

 cells, obtained from cultures in synthetic liquid media (or 

 in a previous experiment from a piece of bark) were dried 

 on barium oxide for 3 months at + 35° ; they were then 

 sealed into glass tubes evacuated to 10"' mm. of mercury, 

 and subjected to -190° for 480 hours and to -269° to 

 - 271° for 71 hours. Some specimens had been kept dried 

 in the vacuum for 25 years before being cooled. In one 

 experiment a temperature of 1.84° K. was maintained for 

 one hour. The material so treated yielded living Pleuro- 

 coccus vulgaris, Chlorella vulgaris, Slichococcus hacillaris, 

 Hantzschia amphioxys, Pinnularia viridis, Chlorococcum 

 humicolum, and Palmella miniala. The same was also 

 true for cultures not subjected to high vacua, but exposed 

 directly to the action of the liquefied gases. 



