AIZOACEAE 201 



Plate 49. 



Mesembrianthemum. 



A. M. obcordellum Haw. 2. Long, section of a twig (corpusculum). 



B. M. calculus Berger, from Van Rhynsdorp. 



C. M. demum Haw., from the Karoo. 



D. M. ficiforme Haw., from Worcester. 



E. M. tigrinum Haw., from the Karoo. 



F. M. bilobum Marl., from Little Namaqualand. 



G. M. digltiforme Thunb., from Van Rhynsdorp. 



Mesembrianthemum. Section Sphaeroidea. 



The plants of this section show a remarkable modification of their 

 leaves. There are generally several shoots from a common root or crown, each 

 one consisting of a short axis and a pair of leaves. The leaves are, however, 

 so completely connate, that they form a single compact body (corpusculum), 

 which encloses the flower bud (Plate 49, A, 2). When the flowering season 

 arrives the bud forces its way out through a short slit at the apex of the flat 

 body and finally opens above it, the ovary remaining hidden within (Fig. 93 A). 

 After flowering the apical slit closes again and the further development of the 

 fruit takes place in the corpusculum, while at the same time a young corpus- 

 culum originates alongside of the ripening fruit, both being supplied from the 

 surrounding parent body with water and food until it is exhausted, its shrivelled 

 remains forming a papery sheath around the new corpusculum. When the 

 fruit is fully developed the stalk stretches itself and raises the seed vessel above 

 the mass of the sheaths, thus enabling the seeds to be scattered more readily. 



Four of the figured plants belong to this section, viz. M. obcordellum, 

 M. calculus (named and described from the above illustration), M. ficiforme 

 and M. bilobum. 



M. tigrinum. This is the type of a group of species (Ringentia) with 

 variously toothed and lobed leaves, from which the specific names have been 

 formed, viz. M. lupinum, caninum, murinum, ermininum etc. The flowers of all 

 these open late in the afternoon and generally close shortly after sunset. 



M. ficiforme. Flowers fragrant, remaining open for several days and nights. 



Mesembrianthemum digitiforme. The specimen figured is merely a twig of 

 a lump as big as a child's head. The corpuscula are very juicy, being filled 

 with a watery, slightly saline sap ; hence they are readily eaten by herbivorous 

 animals in times of drought {fide Mr W. Spilhaus, who brought the entire 

 plant from Van Rhynsdorp). The flowers are remarkably hardy, the petals 

 being stiff and rigid and lasting about a fortnight without any visible change. 



Cultivated specimens of this plant, as figured e.g. by Berger, look so 

 different that they may not represent the same species; but Thunberg's original 

 description in his Flora Capensis agrees so accurately with our plant, that the 

 author had evidently written it on the spot. 



Many other species, when cultivated under less extreme conditions than 

 those they are accustomed to, even at Capetown, alter their habit of growth 



26 — 2 



