100 Knud Jessen. 



it is vertical or obliquely ascending, branches less freely, and 

 the branches are considerably shorter, but they develop ad- 

 ventitious roots as in A. alpina. Undoubtedly, neither species 

 is entirely dependent on the primary root for the continu- 

 ation of life; vegetative propagation takes place. Fragments 

 of the dead leaves persist for a longer time, but in A. alp ina 

 at least the shoots may ultimately get rid of them. 



The leaves are placed in a rosette, but in luxuriant spe- 

 cimens of A. alpina the internodes may be somewhat elon- 

 gated. The first leaf of the shoots — both of the floral and 

 the vegetative — is a scale-leaf in the form of a closed sheath; 

 also the other leaves have closed sheaths which are ruptured 

 on the vegetative shoots owing to growth in thickness. In Ice- 

 land Jonsson found A. alpina with green leaves in the winter. 

 The old leaves had not fallen off, but formed a sort of water- 

 proof roof over the shoots (1. c). In the Botanic Garden in 

 Copenhagen the leaves which remain green through the winter 

 .are, in both the species, very small, few in number and not 

 quite expanded. The summer-leaves wither in the autumn 

 and a few new leaves may grow out, but strictly speaking 

 the plant is scarcely winter-green. The shoot-apices are pro- 

 tected by the closely folding leaf-sheaths; scale-leaves are not 

 developed. 



In the Botanic Garden in Copenhagen there is no fixed 

 flowering-period, but new floral shoots are constantly being 

 developed as in the A. vulgaris-lorms, though not to the same 

 extent as in the latter; and not until the low temperature 

 of winter sets in does the development cease. In December 

 all transitional forms are found, from flowering shoots to 

 quite young buds which are hidden by the leaf-sheaths of 

 the terminal bud. I am not prepared to state whether a 

 similar proleptic development takes place in Arctic Norway 

 and in Greenland. Norman and Lange record that the flower- 

 ing in these regions ends on September 20 and in August 



