24 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



definition includes the whole Sedum flora of Europe, of Asia (except 

 the series Japonica, which is with very few exceptions tender, and a 

 few others), and one (S, multiceps) of the endemic African species, 

 also the Sedum flora of Canada and the United States ; the large 

 Mexican group being treated as tender, though one or two are nearly 

 hardy. 



The hardy category includes the whole of the Eurasian groups 

 Rhodiola, Pseudorhodiola, Telephium, Aizoon, most of the Eurasian 

 Seda Genuina except the Japonica series, and several species of the 

 Sempervivoides and Epeteium sections, which consist of annual or 

 biennial plants. 



The half-hardy and tender Sedums which are in cultivation belong 

 to three geographical groups. They include a small portion of the 

 very rich Sedum flora of Asia ; the greater part of the remarkably 

 varied Sedum flora of Mexico and the lands which border it ; and a 

 couple of species from the Atlantic Islands off the coast of Africa. 



In many respects the tender group differs as a whole in character 

 and affinities from the Eurasian and North American plants which 

 constitute the hardy Sedums. 



Mexican Species. 



The Mexican Sedums (with which may be included a few related 

 species from the south-western United States), which form the largest 

 group among the tender species, present an array of forms bewildering 

 in their variety, and many of them not easy to place in any scheme 

 of classification adapted to the Sedums of the Old World (which con- 

 stitute the bulk of the genus) . The sections Rhodiola, Pseudorhodiola, 

 Telephium, and Aizoon (the first and third of which have represen- 

 tatives in the United States) are absent. But there are present a 

 number of species, which, though possessing no other affinity with these, 

 agree with them and differ from the Seda Genuina in having stems 

 which die back to the rootstock after flowering. These stems are 

 mostly but not always annual, usually arising in summer or autumn 

 and lengthening to a varying extent, resting during the winter, and 

 flowering and dying in the following spring or summer. The rootstock 

 is sometimes large and fleshy, as in some members of the Sedastrum 

 group, more often small, with a tuft of fibrous roots. The flowers 

 are mostly white, but one species has red and one yellow flowers; 

 and the stems and leaves exhibit considerable variety. Neverthe- 

 less, the growth-form is distinctive; they are best classed together 

 as a separate section, Mexicana. 



The bulk of the Mexican species fall under the section Seda Genuina 

 of Koch, but display a much wider range of form than is found in 

 the Old World. A tendency to shrubbiness, as seen in the Old World 

 in S. populifolium Pallas from Siberia, and in a reduced measure in 

 S. multiceps Coss. & Dur. from Morocco and S. variicolor from China, 

 is well developed in many Mexican species, many of them forming 



