TRANSACTIONS 



BOTANICAL SOCIETY OF EDINBURGH. 



SESSION LXXXI. 



On the Affinities of Sedum Praegerianum, W. W. Sm., 

 WITH A Tentative Classification of the Section 

 Rhodiola. By R. Lloyd Praeger, B.A. (Plates II-I V.) 



(Read 8th February 1917.) 



Sedum Praegerianum, W. W. Sm. (Plate II, figs. 1-3), 

 collected in the Chumbi Valley, Tibet, in 1912, and in 

 cultivation at Edinburgh (and, by the- kindness of Professor 

 I. Bayley Balfour, in my own garden), presents several 

 features which, singly or in combination, are unusual in 

 the genus to which it belongs. The erect root-stock is very 

 short, and does not lengthen appeciably with age ; it 

 produces, below, thick fleshy roots recalling those of the 

 Rhodiola section, and, above, a flat rosette of stalked 

 lanceolate entire leaves, which fade in autumn. From the 

 axils of these leaves the flowering-shoots develop in 

 summer ; these latter are prostrate, slender, and leafy, and 

 terminate in a loose cyme of rosy flowers which are 

 egg-shaped (fig. 2), the petals being very erect and almost 

 touching at the tips. 



As stated above, the root-stock, in spite of its abbreviated 

 form, recalls that of the Rhodiola section, in which it is 

 always thickened and usually elongate. The rosette of 

 leaves which crowns the short root-stock is very unusual, 

 and in the genus is found chiefly in certain annual or 

 biennial species, such as the European S. Cepaea, Linn., 

 the Caucasian Sempervivoides group, and some of the 



TEANS. BOT. SOC. EDIN. VOL. XXVn. 9 



