27 



visae for 108 hours to - 70° and for a further 20 hours to 

 - 130°, after which the organisms were no longer capable 

 of raising bread, although no alteration, microscopically 

 visible, could be detected. 



Doemens {Allg. Brau. u. Hopf. Ztg., 2, 2225, 1897) 

 reported that, when he exposed a suspension of yeast to 

 liquid air and thawed it too rapidly in water, the power 

 of development was impaired. 



3. Monocellular Algae. It may be mentioned here that 

 several species of monocellular algae are found in the 

 encysted form in snow and give it a green or red colora- 

 tion. These organisms become active in the melting 

 snow. It is reported that some of them cannot resist 

 temperatures higher than 4°. We did not find any data 

 on the lower limit of temperature that they can support. 

 For the literature on this subject, we refer the reader to 

 a series of papers by Kol, E., and Chodat, F., in Bull. Soc. 

 Bot., Geneve, 25, 1934. 



According to W. West and G. West, Closterium (a des- 

 niid) was found motile in water which had been frozen for 

 14 days. Microsterias (another desmid) was also found 

 alive under the same conditions. Since this last genus 

 was not observed in the cultures in the spore form, the 

 authors remark that it resisted freezing in the vegetative 

 state {Ann. of Bot., 12, 1898, p. 33). 



Wisloucli (1910) exposed SticJwcoccus bacillaris, in 

 sterilized water, to various degrees of cold. A very small 

 number of cells survived a 2 hour exposure to - 75°, while 

 about 50% resisted a 6-7 hour exposure to -21°. 



According to Pictet (1893), various species of diatoms 

 in water cultures, frozen at about - 200°, were uninjured 

 and, after the thawing of the medium, they were seen to 

 extend pseudopodia-like protrusions. 



Edlich (1936) subjected Pleurococcus vulgaris, Apafo- 

 coccus minor and SticJwcoccus hacillaris on their natural 

 bark substratum to temperatures ranging from -20° to 

 -80° for varying lengths of time, after a previous ex- 



