28 Knud Jessen. 



polar and is found in addition in Alpine regions in the tempe- 

 rate parts of Asia, America and Europe. 



The alcohol material is from northern Norway and from 

 Greenland. 



Pot. nivea has a multicipital main root, which may attain 

 a considerable length, at least 60 cm. (Warming's notes) and 

 may also become very thick (6 or even 9 mm.). The often 

 numerous shoots are usually short and close-set, so that they 

 form compact tufts which may attain a diameter of at least 

 20 cm. The shoots are covered by the old, brown leaf-sheaths 

 which, however, disappear in the course of the following 

 years. Sometimes looser tufts are also found; Warming, in 

 his notes, even mentions short, horizontal shoots. In the 

 Botanical Museum in Copenhagen I have measured obliquely 

 ascending shoots which were about 10 cm. in length. Ad- 

 ventitious roots, which are even fairly strong (about 2 mm. 

 in diameter), are frequently found, and it must undoubtedly 

 be presumed, as Warming also is of opinion, that new indi- 

 viduals may be formed by vegetative propagation. The 

 floral shoots are lateral; in a small tuft gathered on Dan- 

 marks in East Greenland at the end of the winter the 

 young floral shoots were found to be subtended by dead leaves. 



The leaves wither in the autumn, but in favourable localities 

 in southern regions a few small new leaves may protrude a 

 little before the winter owing to the fact that the plant has 

 no real winter-bud with scale-leaves. According to Hartz, 

 in Scoresby Sound in East Greenland it lives through the 

 winter in places free from snow. 



Anatomy. The absorbent roots contain fungal hyphæ 

 in balls in the cells of the few-layered, loosely built cortex. 

 The structure of the epidermis and the exodermis is as in 

 Pot. emarginata; but the walls of the exodermis are some- 

 what weaker than in the latter species. In the primary root 

 the secondary woody portion is at first continuous, and not 



