where indicated by arrows. This somewhat elaborate arrsngement 

 of its structural detsils would seen to indicate that the cliloro- 

 phyll of these plrnts is more sensitive to liglit or raore liable to 

 be injured by its intensity then that of their allies, which have 

 not got this window-like structure. N. S. Bpown 



(To be continued.) 



Mesembr^/"9nthemum and some new genere separated from it. 

 Gsrd. Ghron. HI. 70 : 273. 1921.' 

 (Continued from page 250.) 



There is one other snecies of i^'esembryanthemum, the curious 

 *'. rho'^alo^hyllum, which, nlthour'i hrvinp- nothing in common with 

 the I'. I'esliei ^rours, nor any resemb].ance to the, si so belongs 

 to the '"-indovred rjlpnts," and the few others thet sre at present 

 kno'^^n helon"- to the order I'ilipceae. 



One o:^ the most odd-l'^okine- groups placed under ^-esembryenthe- 

 mum is that to which J.!, pubescens and its allies belong. Of these 

 Plants very little is knovTi in this country. They are dwarf tuft- 

 ed rlents, whose grovrths are obliquely elongated, ovoid, or nearly 

 cylindric, and composed of tv;o leeves very unequf 1 in size, one 

 being half or less thr. n hclf as long as the other end combined 

 with it into a single body, except a very short, free portion, 

 which (except ivhen ? new growth is being formed) is so closely 

 pressed rgeinst (or n^-nprently into the side of) the larger leaf 

 ?s to be only distinguisheble by n mere crrck. 'Aiis give to e&ch 

 groivth the ap^eerance of hevinff an oblioue, closed mouth ofx one 

 side o:^ it, so that the growths of these plants as ne--" rly resemble 

 ? shark's head es I think it possible for any pi&nt to do. This 

 ^roup is so distinct in appesrnnoe from ell others placed under 

 -esembr-"T"themum thst although I have not yet seen a flower of any 

 ST^ecies belonging to it, I feel sure that ^^av./ort^ v;as right in 

 considering it to be a distinct genus. I therefore adont the gen- 

 eric name ^ibbaeum he r^ro^osed for it in 1821 (l^evisiones I'lantarum 

 3ucculent8rum, p. 104), which, like some other genera he proposed 

 in the seme book, has never been taken up nor even noticed by any 

 author. The curious resenbl-nce to a sherk's head is well shown 

 in ^ig. 121, which represents e new species of this group, 

 '^ibbseum ar^enteum, described below, of rather more than half 



* '^ibbaeura argenteum, N, E, Bpown. Tufted, V'/ith numerous 

 'growths -^orminp- clumps up to 3 or 4 inches in diameter, =^nd 1 to 

 1^ inch high. Growths about 1 inch long, and 5 to 6 lines thick, 

 cylindric-ovoid, slightly bulging on one side at the lower part, 

 n^pro^'in,"- ui^^'ard to the slir'htli'' compressed, very obtuse apex, 

 obscurelv or scarcely keeled, with an oblique arched fissure 2 to 4 

 lines deep, end 4 to 5 lines broad, resembling a mouth r little 

 beiov; tbe middle, each erov.'th thus somev/hat resembling a shark's 

 heed, vith the v-hole surface silvery-white (becoming greener under 

 cultivation) from being densely covered with short, fine, eppressed 

 heirs, all pointinr do^"mv-ards Flowers unknov.Ti. I^ruiting pedicels, 

 ^ to* inch long. Capsule i inch in djameter, 6-valvedj v/hite,. 

 South Africa, Ladvsmith Civ., on stony ground, a fev» miles form 

 Ladvsmith, Pole Evans, 6932. 



n.-.turf 1 size, from a photograph teken by its discoverer. 



■•-. ^. 



