232 



many — years, especially in S. oppositifolùi ; in .S'. aizoides it 

 undoubtedly dies more quickly, in tlie course of a few years; 

 this feature should probably be connected with the fireater 

 dampness of the habitat. In both species adventitious roots 

 occur, and vegetative propagation takes place by the shoots 

 becoming independent. S. oppositifolia has a tendency to 

 become a sub-shrub, as its stems become more woody than 

 do those of S. aizoides. 



II. The leaves of the vegetative shoots are in all the 

 species foliage-leaves. Buds, protected by true scale-leaves, do 

 not occur. Only in those species which have bulbils and 

 runners, do scale-leaves occur. Sometimes several, sometimes 

 a few, leaves remain alive and green (or reddish) during winter; 

 the following species have been noted as evergreen : — S. aizoides^ 

 Aizooii, cernua, groenlandica, Hirculus, hieraciifolia, nivalis, 

 oppositifolia, stellaris, and tricuspidata. But they are not ever- 

 green to the same extent, and this is probably also dependent 

 in part on the nature of the locality. 



The old, dead leaves persist for a long time upon the 

 stems of some of the species, especially upon those which 

 belong to the driest habitats (e. g. S. tricuspidata, S. groen- 

 landica, S. oppositifolia, and S. Aizoon). 



III. The flowers are developed the year previous to that 

 in which they open, in perhaps all the species. This has been 

 observed in the following: — S. groenlandica, S. hieraciifolia, 

 S. nivalis, S. oppositifolia, and S. rividaris. 



They are so fully developed that both stamens and pistils 

 are distinctly formed, but pollen is scarcely formed, nor are 

 the ovules developed. S. oppositifolia is the most developed. 



There is undoubtedly a .causal connection between this and 

 the fact that the vegetation-period of the plants is so short in 

 Arctic countries: the flowering of the plants must as a natural 

 consequence be placed in early spring to enable the seeds to 

 get sufficient warmth to ripen. 



