Rosaceæ. 



19 



Fig. 6. Potentilla tridendata (From Christianshaab in Greenland). 



A, Transverse section of leaf; both the tangential walls of the upper epidermis are mucila- 

 ginous. ]i, Epidermis of the upper leaf-surface, a stoma is seen surrounded by small cells. 

 C, Epidermis of the lower leaf-surface. D, Section parallel to the surface of spongy parenchyma 

 from the middle of the leaf between a pair of bundles. E and F, Two glandular hairs from the 

 lower leaf-surface. G, Longitudinal section of leaf-stalk through the sone when- the leaf- 

 blade is cast orf ; b. bast ; ch, collenchyma ; /, the basal portion of the leaf : st, stalk ; 

 z, xylem. H , Fragment of a transverse section through the periderm of a rhizome ; k. cork- 

 layer, the striation of the walls is not so distinct as shown in the ligure ; p. phellôid-cells ; 

 the upper side is the outer. (A, B, C, D, E. F and // -'-" f, Q " i). 



2* 



