105 



very high degree, if it had intercellular spaces which were not 

 protected. In regard to leaves which persist for several years, 

 it may be said that the 

 degree of protection is with- 

 out doubt in proportion to 

 the size of the air-cavity. 

 To what degree the air-cavity 

 and the large intercellular 

 spaces serve to utilize the 

 oxygen formed by assimila- 

 tion of the carbonic acid 

 formed by respiration ! am 

 not able to say. The leaf 

 is also protected by different 

 kinds of hairs (cf., e. g., 

 Warming, Biol. Optegnelser, 

 p. 53). 



Jdngner's ^ theories re- 

 garding the importance of 

 the form of the leaf may 

 doubtless be regarded as 

 extremely fanciful. 



Fi£ 



21. Cassiope tetragona. 



Stem. X 180. (Phot.) 



Cassiope liypuoides (L.) Don. (Fig. 22.) 



BöRGESEN, 1895, pp.236 — 237. Tedin, 1892, p. 75. Hessel- 

 man, 1900, p. 27. 



The specimens I have had for investigation are from the 

 following localities: — West Greenland: tent 16 (July 28, 1887, 

 С Ryder); loc. ign. (Aug. 1, 1892). East Greenland: Dronning 

 Louises (Aug. 8, 1885, Eberlin). [Sweden: Åreskutan (Aug. 12, 

 1890).] 



This species belongs to that group of the Cassiope 



1 JuNGNER, Klima und Blatt in der regio alpina. Flora, Bd. 79, 1894, p. 219. 



