387 



of which is similar to that of B. nivalis and, as in the latter, 

 the area with the water-pores occurs almost at the margin; 

 stomata are absent from the under side of the leaf-apex. 



The leaf-stalk is reniform in transverse section. There 

 are three vascular bundles; they are without stereom. The 

 cortex often has lacunae, but otherwise resembles that of the 

 stem (Fig. 32, F.). 



R. reptaus L. 



Lit. Lange, 1887. Hartz, 1894, p. 34. Norman, 1895, p. 6. 

 Rosenvinge, III, 1896, p. 240. 



Alcohol material from Greenland (Sophiehamn, 6.8.1883; 

 Monekordhiak, 19.7.1883); Denmark (Fure Sø, 2.9.1910). 



R. reptans from a morphological point of view, is a tran- 

 sitional form between the preceding species and the R. lappo- 

 nicus-lype. In the flowering plant there is a short, erect 

 rhizome which bears a rosette consisting of a few, stalked, 

 linear to linear-lanceolate foliage- leaves, the uppermost of 

 which subtends a principal bud which may develop a floral- 

 stem with elongated internodes the same year as the parent- 

 axis flowers, but which no doubt usually develops only a rosette. 

 I am not prepared to say whether the latter may remain 

 green during winter in Arctic countries; in Denmark it passes 

 the winter in a green condition. 



The more or less filiform aerial stem becomes horizontal 

 with the formation of the first elongated internode. The inter- 

 nodes are highly curved as in R. hyperhoreus. The two-rowed 

 leaves are very similar in form to the rosette-leaves and, like 

 the latter, they have a large sheath ; the uppermost ones 

 are very small, the number of leaves on the straight stem 

 differs much, 1 have in arctic specimens often found 3—5 but 

 14 also occurs; the creeping stem may reach the length of 

 about 50 cm. When the axis flowers it becomes ascending, 

 usually just above the uppermost leaf; the peduncle however 

 often bears a bract. The uppermost leaf upon the horizontal 



