26 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



The remaining Asiatic tender species are few, and various : 

 Chaneti Hamet (section Seda Genuina, but anomalous). 



^ i section Sempervivoides. 



viscosum Praegerj 



formosanum N. E. Brown ^ 



Leblancae Hamet l section Epeteium. 



Someni Hamet 1 



Finally, of the few species of Sedum inhabiting the Atlantic Islands, 

 two are in cultivation belonging to the section Seda Genuina — 

 S. lancerotiense Murray, and 5. nudum Alton. 



The only large geographical region where Sedums occur not repre- 

 sented in the species known in cultivation is Central Africa, where 

 a few interesting species are found on high mountains (see p. 6). 



X. Description of Species. 



SECTION I.— RHODIOLA. 



Section Rhodiola ScopoH, " Introd. ad Hist. Nat.," 255, 1777 

 {char. ampl.). Praeger in Trans. Bot. Soc. Edinh., 27, 107, 1917. 

 Rhodiola Linn., " Genera Plantarum," ed. i. 318, 1777 {pro genere). 



Perennial. Caudex fleshy, crowned with leaves with a broad 

 clasping base (often reduced to membranous, deltoid or semi- 

 orbicular scales, or becoming so with age) from the axils of which leafy 

 flowering-shoots are produced. Flowers 4- or 5-partpd, dioecious or 

 hermaphrodite. Hardy plants, mostly Asiatic. 



Linnaeus founded his genus to include a single species, R. rosea, 

 the well-known Roseroot. Scopoli reduced Rhodiola to a section 

 of Sedurn, and most authors have followed him in this. While some 

 have limited Rhodiola to species which, like roseum, have unisexual 

 and 4-parted flowers, others have included plants like S. crassipes, 

 which have hermaphrodite 5-parted flowers combined with the 

 characteristic thick scaly Rhodiola rootstock. I have endeavoured * 

 to show that a continuous series of forms leads from the roseum type 

 with dioecious 4-parted flowers, poorly developed scales, and massive 

 rootstocks, through others with hermaphrodite 5-parted flowers and 

 larger scales with a leaf-like tip, to forms like S. Praegerianum and 

 S. primuloides, with hermaphrodite flowers, well-developed leaves 

 instead of scales crowning the rootstock, and short or slender root- 

 stocks. Some members of each group are in cultivation. 



Series I. Rhodiolae sensu stricto. 



Flowers usually unisexual and 4-parted, caudex usually elongate 

 or greatly thickened. Carpels usually short and crowned with short 

 styles reflexed in fruit. 



* Prakger, " On the AflRnities of Sedum Praegerianum W. W. Smith, 

 with a Tentative Classification of the Section Rhodiola." Trans. Bot. Soc, 

 Edinb., 27, 1917. 



