62 



Knud Jessen. 



notes as regards D. integrifolia in Greenland, that it grows 

 in flat, low tufts, usually almost circular in form and about 

 a foot or so in diameter. Each tuft has a strong main root, 

 and a few slender, weak adventitious roots arise from the 

 branches. From the upper end of the main root the branches 

 proceed laterally in a horizontal direction, and they may 

 become fairly long. It hardly propagates vegetatively. — 

 In D. octopetala from Russian Lappmark Kihlman (1. c.) 

 measured branches which were about two metres in length. 

 Haglund ascribes to D. octopitala a rich formation of adven- 

 titious roots from the prostrate parts of the shoots, according 



to him it is almost exclu- 

 sively the adventitious roots, 

 which provide the older in- 

 dividuals with nourishment; 

 he has not been able to 

 find a persistent main root. 

 Schröter records a rich 

 supply of adventitious roots 

 from the under side of the 

 branches of D. octopetala in 

 the Alps. InW arming's notes 

 we read further as regards D. integrifolia: "The shoots are 

 close-set and among them masses of dead leaves are found 

 which persist several years; it grows in its own remains; the 

 fresh shoots are seen in the midst of the blackish brown re- 

 mains of old leaves. Large patches may be found dead in a 

 tuft, but the leaves are still densely crowded." 



The young seedling of D. octopetala has been described by 

 Haglund and Sylvén; it forms a rosette which is provided 

 with a main root and which sooner or later develops lateral 

 shoots. The structure of the shoot of the full-grown plant 

 has been treated by Haglund (loc. cit. p. 7) who, how- 

 ever, doubtfully refers Dryas octopetala to dwarf shrubs 



Fig. 24. 



Leaves of a form intermediate between Dryas 

 octopetala and D. integrifolia collected at Kin- 

 gigtok in Vaigat by Hartz. All the six leaves 

 were found on the same plant, and the dif- 

 ferent forms were represented almost to an 

 equal degree (about natural size). 



