150 Carsten Olsen: Cornaceæ. 



missing in poorly developed plants, e. g. in the specimens 

 from Greenland. 



The anatomic structure of the rhizome and the root is 

 exactly like that of С suecica. Tannin is present throughout 

 the plant. 



The mycorrhizas of С canadensis and C. suecica are 

 alike. 



Summary. 



Cornus suecica is a distinct mesomorphic plant which 

 completely lacks xeromorphic characters; such are however 

 found in C. canadensis; the epidermal cells of the leaves of 

 this species have thickened outer walls, which is correlated 

 to the fact of the 1 eaves being perennial. The more loose 

 construction of the mesophyll of Arctic plants mentioned 

 by Børgesen ^ does not apply to the species here dealt 

 with; on the contrary, the Arctic specimens of C. suecica 

 have a mesophyll of a much closer structure than the spec- 

 imens from more southerly localities. Besides this, the 

 leaves of С suecica, grown in Arctic localities, are disting- 

 uished by being smaller, but decidedly thicker than those 

 of specimens from Denmark. The spongy-tissue is very 

 strongly developed in Arctic specimens. 



^ Bidrag til Kundskaben om arktiske Planters Bladbygning (Bo- 

 tanisk Tidsskrift, Bd. 19, 1895; also in "Journal de Botanique", 

 vol. 9, Paris 1895). 



