34 



NATURAL HISTORY OF PLANTS. 



B. 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 2 dehiscing by two longitudinal clefts. The gynpeceum 

 is superior; 3 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. 4 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, 5 furnished with a very small aril, 6 an 



Rivina humilis. 



V* ft 



Fig. 49. 

 Seed (f ). 



Fig. 47. 

 Diagram. 



• Fig. 50. 

 Longitudinal section of seed. 



annular embryo, with unequal cotyledons enveloping each ether, 7 

 and surrounding a central farinaceous 3 albumen. The Rivinas are 

 suffrutescent plants, natives of warm and temperate America; 9 seven 

 or eight species 10 are distinguished. Their stems are erect or rarely 



1 These two species, which are distinguished 

 moreover by a short style, a penicillate stigma, 

 and climbing stems, form the section Yillamilla 

 (Moq., Prodr., 10). 



2 The pollen is " transparent, spherical, divided 

 by linear bands, like a pentagonal dodecahedron,, 

 in the R. brasiliensis, humilis" (H. Mohl., in 

 Ann. Sc. Nat., ser. 2, iii. 330). 



a There is only one anterior carpellary leaf. 



'' It has two coats. 



5 Those of 11. humilis are : an epidermis with 

 long pointed papilla 1 , 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. 



6 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. 



8 Granular in R. humilis. 



9 "An in India or. indig. ?" (Moq.) 



10 L„ Spec., 177; Mantiss., 41. — Mill,., Diet., 

 v. 611 (Piercea). — Nocc, in Vsler. Ann., vi. 63. 

 — Schead., Gen. III., 17, t. 5.— H. B. K., Nov. 

 Gen. et Spec, ii. 183.— Rot. Mag., t. 1781. 



