1916-17.] BOTANICAL SOCIETY OF EDINBURGH 109 



were found, some of thein not even specifically distinct (in 

 the ordinaiy sense) from true Rhodiolas, and all having 

 the characteristic Rhodiola facies, which were pentamerous, 

 and polygamous or liermaphrodite. The Linnaean defini- 

 tion, in fact, did not separate out a natural group. A 

 better definition was clearly to be based on the growth- 

 form — the thick caudex crowned with scales from the 

 axils of which arise simple leafy annual flower-stems, 

 whether these flowers are dioecious and tetramerous (these 

 two characters generally, but not always, going together), 

 as in *S^. roseum, Scop. (*S^. Rhodiola, DC), 8. elongatwm, 

 Wall., and S. himalense, D. Don, or hermaphrodite and 

 pentamerous, as in ^S*. crassij^es, Wall. (S. asiaticum, 

 auct., nee DC), S. linearifolium, Royle, and S. triflduin, 

 Wall. It seems better to follow Ledebour and Maximowicz 

 in using the term Rhodiola in this wider meaning, than 

 Boissier and Hooker (in Journ. Linn. Soc, Bot., ii, 95) 

 who use it in its restricted sense. The growth-form 

 referred to separates all the Rhodiolas from other Sedums. 

 It is most nearly approached in the section Telephium and 

 in some species of the series Aizoonta of the section 

 Seda Genuina (e.g., S. Aizoon, Linn, and S. Selskyanum, 

 Kegel) ; in these the caudex is thickened, and similarly 

 gives rise to annual leafy flowering shoots ; but the 

 characteristic scale-leaves are absent, and the shoots arise 

 either from the axils of the lowest leaves of the previous 

 season's shoots, or from indefinite points on the caudex 

 near the base of the former shoots. 



In this wider sense, then, the section Rhodiola is 

 characterised by its mucb thickened and usually elongate 

 caudex, crowned with scales, from the axils of which arise 

 unbranched leafy flowering shoots. In some of the more 

 familiar members of the section, such as S. roseum, Scop, 

 and its allies {heterodontum, H. f. et T., Kiriloiui, 

 Regel, etc.), these scales are not very well developed ; they 

 are short, broad, and dry and membranous from an early 

 stage. But in certain other species, belonging both to 

 restricted Rhodiola and to that group in its wider sense, 

 the scales are much better developed, and a study of 

 them throws light on the question of the affinities of 

 S. Praegerianwm. When these Rhodiolas are mature, with 



