280 



the former having less markedly difîerentiated palisade-tissue 

 than the latter. This somewhat indistinct diflferentiation also found 

 by me in the Arctic specimens of S. Cotyledon at my disposal agrees 

 closely with characters found by Bonnier in Arctic specimens; 

 the same investigator (Rev. gén. d. bot., Tome VI, p. 514) has 

 demonstrated this feature very distinctly in S. oppositifolia (see 

 below). His figure of the Arctic leaf of this latter species is good 

 and agrees closely with the results of my investigations. 



Saxifraga Aizoou Jacq. (Figs. 25, 26 and 27). 

 Saxifraga Aizoon Jacq. occurs upon sunny cliffs, and 

 sometimes upon rather wet moraine, and is xerophytic. Its whole 



Fig. 25. Saxifraga Aizoon. 



The leaf: A (2/i)_ Leaf-form. B, Epidermis of the upper surface. C. Marginal hairs. 

 D, Longitudinal section (="/i). 



