476 Fr. J. Mathiesen. 



affords some protection to the winter-buds (M. Porsild in 

 litt.). According to the same author, in the same locaHty, 

 the species flowers 1 — 2 weeks before P. hirsuta (1920, 

 p. 143). On Spitzbergen, according to Ekstam, it is found 

 "auf trockenen, starker Insolation ausgesetzten Abhängen," 



In anatomical respects, the root and stem agree closely 

 with the corresponding organs in P. hirsuta. The anatomy 

 of the leaf is shown in Fig. 41, A — G. In the transverse 

 section 1 — 2 layers of short and broad palisade-cells are seen, 

 and a spongy parenchyma, which consists of distinctly 

 branched cells. В shows a portion of the epidermis of the 

 lower surface, and С a similar portion from the upper sur- 

 face of the leaf. The lateral walls are thin and finely poröse; 

 stomata are found only on the lower surface of the leaf and 

 the guard-cells occur on a level with the leaf-surface. On 

 the basal portion of the leaf, the cuticle is thicker than on 

 the stalk and the lobes, and it is furnished with fine stria- 

 tions. Chlorophyll occur in abundance in the mesophyll, and 

 also in the epidermis of the lower surface. 



The glandular hairs in this species are almost exclu- 

 sively confined to the edges of the leaf-sections; in A is seen 

 exteriorly to the left, a group of the tracheidal tissue in 

 which the branches of the veins end, and in connection with 

 which the glandular hairs occur. The structure of these is 

 similar to that in the other species; the epidermal cell from 

 which the glandular hair is dev^eloped, has not, however, in 

 P. lanata^ much thicker or more highly poröse walls, than 

 have the epidermal cells, which surround it. Non-glandular 

 hairs of the type shown in G occur in abundance on the 

 edges of the leaf-bases, on the stem and, in the floral region, 

 on the scale-leaves and calyx, more scantily on the leaf- 

 stalk, and on the upper surface of the leaf-blade. On the 

 lower side of the leaf-lobes there are small non-glandular 



