Rosaceæ. 31 



(1. c.) in his key of the species in the group Nivea states 

 that among others the present species and P. Vahliana (see 

 p. 34) are destitute of such hairs. The method for discover- 

 ing hairs described by Wolf (loc. cit. pp. 32 and 38) cannot 

 be employed with certainty in the case of leaves with a dense 

 layer of felt as in these two species, when the object is to 

 prove the possible presence of glandular hairs; I have de- 

 monstrated the hairs in transverse sections. 



The leaf-margins are often more or less revolute. The 

 stomata do not occur exclusively upon the lower surface; 

 the few scattered stomata upon the upper surface are 

 situated on a level with the surface, while those upon the 

 lower surface often project slightly (Fig. 10, B). The outer 

 wall of the upper epidermis varies in thickness from about 

 3 to about 4.5 //, in that of the lower it is about 2.5// thick. 

 The radial walls of the epidermis are straight and undulating 

 on the upper and lower surfaces respectively (Fig. 10, C, D). 

 Several of the cells of the epidermis on the lower surface of 

 the leaf have mucilaginous inner walls (see also Kruch). 

 In the leaves investigated the palisade parenchyma consisted 

 of 2 — 3 layers of cells. The thickness of the leaf varied between 

 132« (N. E. Greenland) and 192^ (Norway) and the proportion 

 between the leaf-thickness and the thickness of the palisade 

 parenchyma was |. In the two upper layers of the palisade 

 parenchyma the cells were well-formed; they inclosed large 

 intercellular spaces. The spongy parenchyma was loose in 

 structure and consisted of slightly branching cells (Fig. 10, E). 

 Here reference should be made to Bonnier (1. c.) who in 

 leaves from Spitzbergen found two layers of palisade-cells 

 which were scarcely longer than they were broad. In speci- 

 mens from the Alps he found 3 — 5 layers of palisade-tissue: 

 the cells were narrow and well-formed, and intercellular 

 spaces were either wanting or few in number. 



Warming says in his notes regarding the flowers from 

 Greenland: "The flowers are highly conspicuous on account 



