106 Knud Jessen. 



addition, in northern temperate Europe ^. — The alcohol 

 material is from Greenland, Iceland and the Færøes. 



The young seedling of A. vulgaris is according to Sylvén 

 a rosette, and in older plants also the leaves are always placed 

 in a rosette even if the internodes are often somewhat elon- 

 gated. The rhizome is vertical or oblique or almost horizon- 

 tal, and in the last case there may be a slight wandering. 

 It does not branch so freely as in A. alpina. Even during 

 the year in which it germinates adventitious roots arise, 

 and these are afterwards developed abundantly. 



The floral axes are lateral, and there occurs, at any rate in 

 several of the elementary species growing in Denmark, a similar 

 proleptic development of the floral shoots as in A. alpina in 

 Copenhagen, only the development is more vigorous. It 

 appears to be external factors (e. g. fall of temperature) rather 

 than internal which limit the flowering period; we may be 

 justified in presuming that something similar happens also 

 in the Arctic regions; Norman records that in Arctic Norway 

 A. vulgaris may flower till September 20. 



The plant lives through the winter in a more or less 

 green condition (Warming, 1884; Jonsson and Sylvén); but 

 we may also find it without any green leaves (in Denmark) 

 and as in A. alpina the summer leaves wither in the autumn. 

 The shoot-apex is protected by the sheaths of the foliage- 

 leaves; scale-leaves are not developed. 



Anatomy. — Roots of A. minor and A. acutidens have 

 been investigated; in structure they resemble essentially those 

 of A. alpina and A. færøensis (cf. Fig. 38, В). Mycorrhiza has 

 been found in A. acutidens from Iceland. 



The rhizomes are on an average thicker than those of 

 A. alpina; this is especially due to the fact that the pith is 



'^ See Harald Lindberg. Die nordischen .4Zc/iimi7Za pu/g:a/-ts-For- 

 men und ihre Verbreitung. Acta Soc. Scient. Fenn. XXXVII. 

 Helsingfors, 1909. 



