Rosaceæ. 57 



in the stems from Spitzbergen and Greenland investigated 

 by me. Within the epidermis, which had fairly strong 

 outer walls, I found 1 — 2 layers of weak collenchyma; this 

 was practically similar in the floral region and the rest of 

 the stem, but the degree of development reached by the 

 stereom in these two parts was different. In the floral region 

 there were a great number of primary bundles within a com- 

 mon endodermis; secondary formations were of slight thick- 

 ness only, as no interfasicular cambium occurred. The whole 

 of the pericycle was transformed into bast of medium strength 

 or weaker. In the rest of the stem a complete cambium had 

 formed a considerable amount of secondary w^od consisting 

 chiefly of stereom, and in the pericycle isolated bundles of 

 bast occurred. Here, also, there was a common endodermis. 



Both leaf -surfaces are slightly hairy with compressed, 

 unicellular, thick-walled hairs. Moreover, there occurred on 

 both sides, but in greater abundance on the under side, small 

 stalked glandular hairs of the form shown in figure 22, B. 

 Stomata occur on both surfaces of the leaf in almost equal 

 number; they are sunk below the level of the surface (Fig.22, Л ). 

 The outer wall of the upper epidermis is 3.3 to about 4^ thick 

 and that of the lower about 3/i. The cuticle is uneven. The 

 surface views of both the upper and lower epidermis have 

 almost the same appearance, the radial walls are slightly 

 undulating (Fig. 22, E, F). The inner wall of the epidermis 

 of the upper surface is sometimes mucilaginous (Fig. 22, C). 

 Cells with such mucilaginous walls are often larger than the 

 surrounding cells (this fact is also mentioned by Warming 

 in his "Halofyt Studier")^ and they appear to occur in varying 

 quantities in the different localities; in the leaves from the 

 Botanic Garden in Copenhagen more epidermal cells were 

 found with than without mucilaginous walls. 



The thickness of the leaves showed some variation: 

 1 See p. 59. 



