34 NATURAL HISTORY OF PLANTS. 
R. peruviana. Each is composed of a filament free or scarcely 
united at the base to the neighbouring filaments, and of a two-celled 
introrse anther’ dehiscing by two longitudinal clefts. The gynæceum 
is superior; it is formed of a one-celled ovary, surmounted by a style 
eccentrically inserted towards the posterior edge of the ovary and 
traversed in its whole length by a vertical groove, prolonged into 
the interior of the stigmatiferous head of the style. In the ovary 
cell there is a subbasilar placenta, supporting a single ascending 
campylotropal ovule with the micropyle looking downwards and 
from the anterior side of the flower.‘ To the ovary succeeds a fruit 
which is accompanied at its base by the green perianth and the 
reflexed staminal filaments surmounted by a vestige of the withered 
style. The pericarp is thin and quite fleshy. It contains a sessile 
seed, enclosing under its coats,’ furnished with a very small aril, an 
Rivina humilis. 

Fria. 49. Fia. 47. 
Seed (8). Diagram, Longitudinal section of seed. 
annular embryo, with unequal cotyledons enveloping each cther,? 
and surrounding a central farinaceous® albumen. The Rivinas are 
suffrutescent plants, natives of warm and temperate America ;’? seven 
or eight species” are distinguished. Their stems are erect or rarely 

1 These two species, which are distinguished 
moreoyer by a short style, a penicillate stigma, 
and climbing stems, form the section Vi/lamilla 
(Moq,, Prodr., 10). 
2 The pollen is “transparent, spherical, divided 
by linear bands, like a pentagonal dodecahedron, 
in the À. brasiliensis, humilis” (H. Mout., ir 
Ann, Sc. Nat., sér. 2, iii, 330). 
3 There is only one anterior carpellary leaf, 
4 Tt has two coats, 
5 Those of À. humilis are: an epidermis with 
long pointed papilla, or cellulose hairs, which 
exist already upon the primine, simple or sepa- 
rated towards their summit into two or three 
branches; a testaceous, smooth, black brittle 
envelope; a thin, whitish membrane applied 
directly upon the embryo. 
5 This is a slight whitish or fleshy thickening, 
surrounding the umbilical region (which forms a 
little depression at its centre), and becoming 
slightly reniform in R. humilis, its concave edge 
looking at the micropyle. 
7 Folded twice upon themselves in most of the 
species. 
§ Granular in R. humilis. 
9 & An in India or. indig.?” (Moa.) 
W L,,, Spec., 177; Mantiss., 41.—MItt., Dict., 
v. 611 (Piercea).—Noce., in Uster. Ann., vi. 63. 
ScHRAD., Gen. IU., 17, t. 5.—H. B. K., Nov. 
Gen, et Spec., ii, 183.— Bot. Mag., t. 1781. 

