The Flora of Disko Island and Adjacent Coast of West Greenland. 67 
often occur others which are not due to the ecological conditions, 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 described and named by previous 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 Aretic Willows by C. Kk. 
ScHNEIDER (Botan. Gazette 66-67) came to my knowledge after 
having handed in my MS. to the printer, and consequently | have 
not been able to utilize them here. 
XVI. Betulaceae. 
119. Betula nana L. 
On heath and not too moist bogs. Usually one of the most im- 
portant plants of the heath and in places it becomes dominant and 
plainly forms “‘birch-heath’. Besides forming espaliers against boul- 
ders. Less frequently forming small birch-copses sheltered by willow- 
copses. 
In places, which are warm in summer and sufficiently covered by 
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 
plants of the heath: this is the case as well at 72° n. |. 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 Ntgssuaq peninsula, one may sometimes walk for miles 
without seing a single specimen of Betula. 
It cannot be the climatic conditions which causes this scarcity. 
| should rather think the lack of the commensals necessary for the 
roots was the reason for this. 
The larger specimens are collected 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, but to be searched for north of 74°30’. 
Abundantly flowering and fruiting. 
Hibernates normally covered by snow, but in unfavourable places 
the snow-cover periodically may be absent. 
5* 
