386 



AnDH. LtNDAGKH 



snow is a very coiivciiieiil ("orin lor this, because it alTords a possi- 

 bility of regiilatiui^ the moisliiie diirinf^ the summer. 



Compared \\\[h this, the imi)ortance of the snow as a protecting 

 cover is very subordinate, because this cover is not constant, nor 

 are there many species whicli rely on it, and with regard to which 

 it may reasonably be supposed that they require a snow-covering 

 for their existence in these regions. 



The main result of my measurements really shows me only 

 what was to be expected, that in the summer there may be a con- 



Fig. 6. ///p/)um-association in a lakelet near Danmarks Havn. 



siderably higher temperature in the earth and the water, which is 

 independent of a far lower temperature in the air. And a short 

 period wùth a temperature below zero need by no means prove fatal 

 to the parts of the plant above ground ; but I do not know the 

 temperature which causes the death of the protoplasm, nor whether 

 the same low temperature always has the same effect; presumably 

 the conditions during the thaw also play a rôle in this connection. 

 Further it would be of interest to obtain measurements of the 

 temperature of the living parts of plants during assimilation. 



Even long before the snow-covering disappears, radiant heat is 

 conveyed to the soil below it, as has been proved by measurements 

 taken with a black bulb thermometer. 



On April 27, 1908, between 1 and 2 p. m., the meteorologist of 



