162 



O. Hagerup. 



lations of the perpendicular epidermis walls, on the lower 

 surface, than was the case with leaves from Denmark. The 

 cell (soe Fig. 3g), which carries a glandular hair, has however 

 straight cell walls, and the spongy tissue underneath is without 

 intercellular spaces. The mesophyll has a pretty, regular 

 structure rich in intercellular spaces, especially so in the 

 spongy tissue, but also in the palisade tissue (Fig. 4). 



Fig. 6. The lowermost layer of spongy tissue, viewed from above; 



g, from Greenland ; d, from Denmark. 



The leaves from Denmark had, with scarcely any excep- 

 tion, one layer of short, broad palisade cells only, while those 

 from Greenland had two; further, the spongy tissue of the 

 Danish leaves had throughout a looser structure than those 

 from the Arctic. 



These relations are the opposite to what has been found by 

 examination of other Arctic plants with regard to leaf-structure; 

 the explanation is probably, that Linnaea in Greenland grows 

 on open heaths, and consequently is not, as the Danish 

 plant, a typical shade-plant. 



