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 C. suecica. Tannin is present throughout 

 the plant. 



The mycorrhizas of C. 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 1 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 C. 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. 



1 Bidrag til Kundskaben om arktiske Planters Bladbygning (Bo- 

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

 vol. 9, Paris 1895). 



