231 



B. Nearest to this type come: S. cernua, S. rivnlaris^ 

 S. HircuJus, and ChrysospJenium. Here, also, are developed 

 vertical rhizomes with foliage-leaves in a rosette, but the Pri- 

 ww/a-type is less pronounced, and is combined with the develop- 

 ment of bulbils or of runners with scale-leaves or imperfect 

 foliage-leaves, and adventitious roots. 



C. To the Sempervivuni-lype belong: S. Aizoon and S. fla- 

 gella ris. The principal stem is vertical and bears a close 

 rosette of foliage-leaves; it has many adventitious roots and 

 dies away entirely after flowering. Lateral shoots arise from 

 the leaf-axils in no fixed order, they run more or less hori- 

 zontally along the ground for some distance and terminate in 

 a new rosette. In S. fiagellaris the runner is very slender and 

 consists of a single internode ; in S. Aizoon it is short and 

 includes several internodes. 



D. Species with ^'rhizoma multiceps," a many-headed 

 rhizome, are: S. groenlandica and S. tricuspidata. Their pri- 

 mary root remains alive a long time, which should probably be 

 correlated with the dry localities in which they grow (crevices 

 of rocks and bare stony ground in fell-fields). The adventitious 

 roots, which are few in number, are usually of little importance; 

 vegetative propagation, by the lateral shoots becoming inde- 

 pendent, therefore takes place either rarely or not at all. The 

 principal rejuvenating shoot is usually developed in the axil of 

 the uppermost leaf, and other lateral shoots occur in basipetal 

 succession. The first foliage-leaves of the lateral shoots may 

 become so fully developed, even during the flowering of the 

 parent shoot, that most of the foliage-leaves of the shoot-com- 

 plex consist of them. 



E. To the creeping-herh-lyi^e belong: S. oppositifolia and 

 S. aizoides. The shoots are prostrate, and have their internodes 

 more or less elongated. There is no regularity as regards the 

 situation of their branches; no principal rejuvenating bud occurs. 

 The primary root appears to be able to live several — perhaps 



