2% Mr. J. Miers on the Menispermacese. 



sepals in two series, imbricated in aestivation, three small, ovate, 

 erect petals, and a central stamen almost concealed by the pe- 

 tals. It is, however, in the structure of the stamen that this 

 genus differs essentially from Stephania : in the latter genus the 

 anther has three or six cells, connate in an annular ring, affixed 

 on the margin of a peltate disciform connective, which is sup- 

 ported on the central filament ; these cells always burst bival- 

 vately by a crenated horizontal line of sutures. In Perichasma 

 the anther has no connective, is comparatively large, completely 

 globular, simply 1 -celled, and dehisces by a somewhat small 

 apical opercular valve, which is supported by a columella-like 

 extension of the filament (or placentoid of M. Chatin), round 

 which the grains of pollen are secreted ; the wall of the globular 

 cell consists of a finely reticulated membrane (apparently defi- 

 cient of the usual inner lining or endothecium), is very delicate 

 in texture, without the slightest vestige of any dissepiment 

 or nervure, its three indented furrows being due to the external 

 pressure of the petals which embrace it in the bud. This 

 organization of the anther is without any parallel in the Meni- 

 spermacea, and reminds us of the opercular theca of some of the 

 mosses. 



The generic name is derived from irepX, circum, circa, ^(aaiJba, 

 hiatus, in allusion to the feature just mentioned. 1 have placed 

 it among the Cissampelidea, but 1 am not certain that this is its 

 proper place. 



Perichasma, nob. — Flores dioici. Masc. Sepala 6, biserialia, 

 quorum 3 interiora paululo longiora,oblonga,submembranacea, 

 . demum expansa. Petala 3, dimidio breviora, orbicularia, 

 carnosula, margine membranacea, erecta, sepalis exterioribus 

 opposita. Stamen unicum, centrale ; filamentum tenue, petalis 

 brevius; anthera majuscula, globosa, leviter 3-sulcata, apici- 

 fixa, septorum nullo vestigio omnino 1-locularis, theca tenuiter 

 membranacea et minutissime reticulata, supra medium rima 

 horizontali operculatim dehisCente, operculo parvo, apicali, co- 

 lumella centrali suffulto ; pollen simplex. — Fosm. ignoti. 



Frutex scandens Africa tropica ; rami longe pilosi ; folia alterna, 

 peltata, oblonga, imo truncata, palmati-nervia, margine grosse 

 crenata, sparse pilosa, longe et tenuiter petiolata : infiorescentia 

 ^ supra-axillaris, longissime racemi/ormis, pendula, pcdunculo 

 tenuissimo, puherulo, alternatim ramoso, ramis iterumque ra- 

 mosis, ramnlis plurifloris ; floribus minutis, alternis, pedicellatis, 

 glahris. 



The single species, Perichasma latificata, will be described in 

 the third volume of the ' Contributions to Botany.' 

 [To be cootinued.J 



