SUCCULENT PLANTS. 



453 



S. coeruleum, an annual, is extremely pretty with pale-blue flowers, 

 and S. brevifolhim and S. dasyphyllum are well-known rockery plants. 

 Sempervivums are numerous — S. calcareum, with dark leaf-tips, is often 

 used for edgings, sometimes under the corrupt name S. califomicum ; 

 S. arachnoideum in several varieties is well known, and S. Beginae- 

 Ameliae is a choice form found in Greece. It is quite sufficiently distinct 

 from S. tectorum, to which botanically it is referred. S. atlanticum is 

 an outlier, beyond the Mediterranean, in the Atlas Mountains. . One 

 species, S. arboreum (fig. 71), is remarkable as a native of Europe ; it is 

 f rutescent, and as it grows in Sardinia, Sicily, and Crete (as well as on the 



1 2 3 



4 5 



Fig. 71.— (1) Sempervivu.m strepsicladum ; (2) S. urbicum?; (3) S. arboreum; 

 (4) S. canariense ; (5) S. Haworthii. 



mainland, where it might have been introduced) it seems to suggest that 

 these islands are of oceanic rank and the Mediterranean equal to an ocean. 

 Low herbaceous plants growing on continents are often represented on 

 oceanic islands by shrubby species, and the only other frutescent Sem- 

 pervivums are found in Madeira and the Canaries. It would be of interest 

 to introduce S. mutabile, a native of Crete. 



Madeira and the Canaries. 



In Madeira we find Sempervivum glutinosum and the remarkable S. 

 tabulaeforme,* the leaves of which form a perfectly level disc, and others, 



* I follow the Index Kewensis in referring this plant to Madeira. Lowe, in Flora 

 Madeira, p. 334. says it belongs strictly to the Canaries. 



