266 



Eue. Warming. 



turned inwards, as in Fig. 21, A ; they may also be directed 

 straight out and curved backwards. More decided dorsiven- 

 trality with two layers of palisade-cells on the ventral side, 

 was found in a specimen of Cerastium trigynum from Iceland. 

 Palisade-tissue on both sides I have moreover found 



Fig. 21. Minuartia biflora. 

 A, From N.E.Greenland; 27.6.1908; A. Lundager. B, Transverse 

 section of leaf; the cross-hatched part is the mechanical tissue; the 

 two leaves, C and D, which belong to B, show the venation; the fine 

 dots indicate cells with crystals of calcium oxalate. E, Transverse 

 section of leaf. F, Margin of transverse section of a leaf; to this belongs 

 the more highly magnified G. H, Epidermis of ventral surface. J, Epi- 

 dermis of dorsal surface. K, Transverse section of leaf, centric struc- 

 ture. L, Epidermis of dorsal surface, seen from within, the outlines 



of the air-cavities under the stomata are distinctly seen. 



From N.E. Greenland: A, E, F, G, H, J and L; from W. Greenland 



(Holsteinsborg; 4. 8. 1885; Rosenvinge): B, C, D and K. (E.W.) 



in Honckenya; it was however highest on the ventral side. 

 Stomata occur on both surfaces. According to Heinricher, 



