Tho Flni'ii nf l)isk() Island and Adjacenl Cloast ol' West Greenland. 67 



often occLir others which are nol due to the ecological coiiditions, and 

 they seem to be hereditable constant. 



In every copse of considerable extension several forms occur, 

 now forming small groups, now growing scattered in the copse. 



I have only mentioned above the main-species and none of the 

 numerous varieties doscribed and named by previoiis authors, because 

 ] am well aware of my deficiency of ability and my lack of information 

 and also of my shortage of figures and of properly determined material 

 for comparison. 



The various highly interesting papers on Arctic Willows by C. K. 

 Schneider (Botan. Gazette 66 — 67) came to my knowledge after 

 having handed in my MS. to the printer, and consequently I have 

 not been able to utilize them here. 



XVI. Betulaceae. 

 i 119. Betula nana L. 



■ 



On heath and not too moist bogs. Usually one of the most im- 

 portant piants of the heath and in piaces it becomes dominant and 

 plainly forms "birch-heath' . Besides forming espaliers against boiil- 

 ders. Less freqiiently forming small birch-copses sheltered by willow- 

 copses. 



In piaces, which are warm in summer and sufficiently covered hy 

 snow during the winter and especially in valleys far from the coast, 

 it is able to rise from the ground with the branches above the other 

 piants of the heath; this is the case as well at 72° n. 1. as south at 67°. 



Very common throughout the whole area, though not everywhere. 

 As well at the southern as in the northern part of the area. for instance, 

 on Disko and Nijgssuaq peninsula, one may sometimes walk for miles 

 without seing a single specimen of Betula. 



It cannot be the climatic conditions which causes this scarcity. 

 I should rather think the lack of the commensals necessary for the 

 roots was the reason for this. 



The larger specimens are coUected on a large scale by the natives 

 who use them for fuel. 



Widely distributed in Greenland; the south limit at 63° (Ros.). 

 The northern limit unknown, Init to be searched for north of 74°30'. 



Abundantly flowering and fruiting. 



Hibernates normally covered by sno\\, but in unfavourahle piaces 

 the snow-cover periodically may be absent. 



5* 



