:ViG 



togellier around llic hiiiidles, Imt I diii nol observe any ligni- 

 fied slereom ; on the onter side ol llie sieve-tissue in some of 

 the linndles, from one lo hvo lavers of slif^lilly collenchyma- 

 tously lliicki'ned tissue can be seen. The endodermis is not 

 distinct. Within the V-shaped mass of wood some small- 

 celled parenchyma often occurs. Between the wood and the 

 camliiiiiii there is in this species, as in the others, some 

 wood-parenchyma. The cambium is but slightly developed. 

 Interfascicular, lignided slereom is also absent, but the cells 



Fig. 6. R. glacialis. 



Transverse section of stem (Jan Mayen). A, An entire section from near the base. B, 



Portion of section from ttie middle of the stem, ep. Epidermis; c, cortex; ph, leptome; 



X, xylem; ;, lacuna, (vl, about ^"l\\ B, 'Vi). 



of the medullary rays are smaller and more closely placed 

 than are those of the cortex. The pith is more or less broken 

 down in the stem, while in the peduncle it resembles the 

 cortex in structure, but the lacunæ are still larger. 



Such a loosely-woven stem is able to retain its erect 

 position probably only by reason of its thickness (3^ — 4 mm.) 

 in combination with the pressure of the sap; and the fact 

 mentioned above as recorded by Wydler, that the stem may 

 lie upon the ground with its lower part prostrate, is easy to 

 understand when reference is made to its structure. 



