Mr. J. Miers on the Menispermacee. 267 
27. DissopeTaLumM. 
This genus is proposed for a species belonging to Mauritius 
and Madagascar, long since known, but imperfectly examined — 
the Cissampelos Mauritiana of Thouars, a plant not common in 
collections, but which has been much confounded with others of 
African and Asiatic origin. It differs from Cissampelos in its 
female flowers, which have two distinct petals, placed one on each 
side of a single sepal, so that they alternate with the latter, anda 
solitary ovary. This is admitted by Thouars in his original de- 
scription of the typical plant, where he says the corolla is 2-lobed. 
In Antizoma we also find two petals; but then there are two sepals 
placed immediately behind and opposite to them, and a single 
ovary. In Homocnemia there are four sepals, four petals, also 
with a solitary ovary ; while in J/eospermum we find three sepals, 
and three petals, placed round a central ovary, as in Stephania. 
In the two former the structure of the male flower is like that 
of Cissampelos ; in the two latter it is unknown. In order, there- 
fore, to maintain consistency in so extensive a genus as Cissam- 
pelos, it becomes necessary to maintain the several genera above 
mentioned ; and Dissopetalum claims as high a title to distinction 
as any of them. Its structure must not be confounded with a 
peculiar anomaly I have observed in one species of Cissampelos, 
which might easily be mistaken for a Dissopetalum; it occurs in 
C. testudinaria from the Galapagos, where the petal appears 
double, owing to its being deeply cleft into two equal segments ; 
but on attentive examination it is seen that the two segments 
are seated upon a single claw, fixed to the base of the sepal ; the 
two lobes of the petal are therefore quite anterior and opposite to 
the sepal, not lateral and alternate with it as in Dissopetalum. 
It is probably to this exceptional case that the authors of the 
‘Flora Indica’ allude when they affirm (p, 198) that they have 
several times seen the petal in Cissampelos “bipartite to the base.” 
I have carefully examined and drawn the analyses of many 
hundreds of flowers of Czssampelos, but, with the exceptions above 
mentioned, I have invariably found only a single complete petal 
fixed to the claw of a single sepal. There is seen in the genus 
Peraphora, which will shortly follow, another anomalous depar- 
ture from the normal structure of Cissampelos, where in the g 
flower there are two minute petals, or none at all, and a campa- 
nular sepal, and in the ? two equal saccate sepals, without any 
petal, with an ovary in the centre. 
The name of the genus under consideration is derived from 
the feature of its twin petals; its characters, as far as they are 
known, are thus enumerated ;— 
