(IS 



3. Lichens. Tlic lidiciis arc known lo be plants wliieli, 

 in the natnral condilions, arc anion*;- the most resistant to 

 low toni])t'ratnr('s. Tiicy flonrish in the northern climates 

 and on the hii;h monnlains in the proximity of the 

 glaeiers. 



Jnmolle (181)0 and 1S!)2) attributed the high cold re- 

 sistance of the lichens to their ability to lose water at the 

 onset of the cold season. In confirmation of his views, he 

 gives the fact that the ratio between the fresh wxMght and 

 the dry weight of Phi/scia and Parmelia, collected during 

 the winter, was found to be as low^ as 1.10 to 1.14; also that 

 lichens of the same kind, soaked in water, absorbed an 

 amount of moisture equivalent to 3^ times their weight. 

 But determinations by the same author of the quantity of 

 oxygen and of carbon utilized by lichens previously 

 soaked in w^ater and then frozen resulted in the conclusion 

 that respiration was still active after 8 hours at - 8°, and 

 photosynthesis after several hours at -30° and -40°. 

 The author attributes this activity to the presence of free 

 water, not yet frozen at these temperatures. If a high 

 water content does not increase the injurious effect of 

 freezing, as the second part of Jumelle's work seems to 

 show^, one can hardly see hoW' a natural dehydration could 

 explain the high cold resistance, as it is assumed in the 

 first part. 



According- to Becquerel (1932d), lichens of the genera 

 Parmelia, Xanthoria and Cladonia, desiccated in the air 

 and exposed for 18 days in liquid nitrogen, became green 

 again when brought back to favorable conditions, their 

 gonidia resumed grow^th, 



4. Mosses. Irmscher (1912) studied the cold resistance 

 of about 34 species of mosses belonging to 27 genera. The 

 gametophytes, freshly gathered, were put into tubes 1.5 

 cm. in diameter, and the tubes immersed for 18 hours in 

 an ice-salt freezing mixture at - 5°, - 10°, - 15°, - 20°, and 

 -30°. Two i)ai'allel series of experiments were carried 

 on, one in which the material was in air, the other in 

 which it was in water. The leaf cells were then tested for 



