162 



О. Hagerup. 



lations of the perpendicular epidermis walls, on the lower 

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

 cell (see Fig. 3^), 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). 



or d 



Fig. 5. 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. 



