Rosaceæ. 55 



more or less covered by the dead shoot- and leaf-masses of 

 the tuft; they branch freely and often have a characteristic 

 appearance on account of the lateral shoots often arising al- 

 most at right angles. The internodes are usually short, and 

 Kjellman refers Sibbaldia prociimbens to one of the charac- 

 teristic types of rosette-plants; in vigorous specimens from 

 the Botanic Garden in Copenhagen the internodes are, how- 

 ever, as much as about one cm. long. The leaf-arrange- 

 ment is two-rowed. The dead parts of the leaves persist 

 for a )ong time on the shoot and may impart to the latter 

 a peculiarly scaly appearance especially in its older parts; 

 or the shoot becomes quite smooth owing to formation of 

 periderm. 



The floral shoots with the compact inflorescence are 

 found during summer subtended by dead leaves which are 

 seated below the living terminal rosette. Often 2 — 3 floral 

 shoots are developed on the same branch. As is the case 

 with the vegetative shoots, they vary greatly in size accor- 

 ding to the nature of the habitat; in much exposed places 

 they attain a length of 1 — 2 cm. only, — Plants which Hartz 

 collected at Scoresby Sound in the autumn had vegetative 

 lateral shoots of the same year in which a small foliage-leaf 

 had unfolded; in the Botanic Garden in Copenhagen this 

 proleptic development is more pronounced. The new shoots 

 begin either with a scale-leaf or with a weak foliage-leaf. 

 Afterwards no scale-leaves are developed, and the shoot- 

 apices are protected by the older, closely folding leaf-sheaths. 

 The leaves wither in the autumn — at least in the Botanic 

 Garden in Copenhagen. - 



Anatomy. The primary structure of the adventiti- 

 ous roots of the first and second order is practically the 

 same, with the exception of the central cylinder which in the 

 former is triarch-tetrarch and in the latter diarch. But the 

 outer walls of the epidermis of the lateral roots are somewhat 



