346 



together around the bundles, but I did not observe any ligni- 

 fied stereom ; on the outer side of the sieve-tissue in some of 

 the bundles, from one to two layers of slightly coUenchyma- 

 tously thickened 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 

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

 wood-parenchyma. The cambium is but slightly developed. 

 Interfascicular, ligniûed stereom is also absent, but the cells 



ep 



Fig. 6. R. glacialis. 



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



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



X, xylem; I, lacuna. {A, about -'"Д; В, "/i). 



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 lacunae 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. 



