AN ENCYCLOPAEDIA OF HORTICULTURE. 



535 



Ourisia continued. 



September. I. mostly radical, oval or oblong, unevenly but not 

 deeply notched. //." 6in. to 12in. Andes of Cliili, Ic62. See 

 Fig. 788. (15. M. 5335.) 



FIG. 788. OURISIA COCCINEA. 



O. Pearcei fPearce's).* ft. crimson, streaked with deep blood- 

 red, tubular, two-lipped, several to a scape. I. ovate, coarsely 

 crenated, purplish beneath. Chili, 1863. A handsome species. 

 (F. M. 154.) 



OUROUPABIA. 



Be). 



A synonym of Uncaria (which 



OUVIRANDRA (from Ouvirandrano, its native 

 name, said to signify Water-yam ; the roots are edible). 

 ORD. Naiadacece. A small genus of stove aquatics, with 

 tuberculate roots, now included, by the authors of the 

 " Genera Plantarum," under Aponogeton. The chief 

 interest of these plants lies in the remarkable singularity 

 of the leaves. The water in which the species are grown 

 should not be above l|it. deep. A compost of loam and 

 < ecayed vegetable matter, in equal parts, is most suit- 

 able. The temperature of the water should not ex- 

 ceed 75deg. Propagation may be effected by seeds, or by 

 divisions of the root. The plants, when properly grown, 

 generally sow their own seed. 



O. Bernieriana (Bernier's). fi. pink, the flower-stem divided 

 into four spikes at the apex. August. Stem much inflated about 

 the middle. Madagascar, 1858. This species resembles the 

 better-known 0. fenestralis in general structure ; the leaves, bow- 

 ever, are much narrower and longer, and the nerves are much 

 closer. (B. M. 5076.) 



O. fenestralis (window-leaved).* Lace-leaf or Lattice-leaf Plant. 

 jl. greenish-white, the flower-stem split at the top into two 

 soikes. August. 1. 6in. to 18in. long, and from 2in. to 4in. broad, 

 oblong in shape, with an obtuse apex, and spreading out nearly 

 horizontally beneath the surface of the water. The leaves them 

 selves are merely a network of vascular tissue, resembling lace 

 or a lattice-window. Madagascar, 1855. A most singular plant. 

 (B.M. 4894.) 



OVAL. Having the figure of an ellipse. 



OVARY. The part of the pistil that in the flower 

 incloses the ovules, and in the fruit incloses the seeds. 

 Its true nature will be best understood if we examine 

 the flower of a garden Pea, or of any similar plant. In 

 the centre of the flower, hidden from view by the lower 

 petals, and by a tube formed of the united stalks (fila- 

 ments) of the stamens, lies the pistil, which, in the 

 order Leguminosce, to which the Pea belongs, consists of 

 a single carpel. To expose it to view, the petals and 

 stamens must be removed ; it is then seen to have the 

 form shown in Fig. 789. The part next the stalk (o) is 

 broader and greener, and, on being slit open, is found 

 to contain two rows of small bodies, which are the 

 ovules: this part is the Ovary. It becomes narrowed 



Ovary continued. 



rather abruptly into a paler body (s), which is called 

 the style, and which bears at its tip, and for a little 

 i distance down the hollow side, a part (st) called the 

 stigma, suited by its structure to receive the pollen 

 grains, and to permit of their fertilising the ovules 

 through it. By comparing a ripe pea-pod (Fig. 790) 



FIG. 789. PISTIL FROM FLOWER OF PEA A, From the side, 

 natural size, showing (o) Ovary, (s) Style, and (st) Stigma. B, 

 Pistil opened lengthwise, to show a row of Ovules along 

 the Placenta. C, Cross section to show position of Placenta. 



with the carpel of the flower, it will bo found that the 

 Ovary has increased very much in size, and that the 

 style and stigma have shrivelled to a mere shred (s) on 

 the tip of the pod, but no new parts can be dis- 

 tinguished. The ovules have developed into seeds. In 

 such a carpel as a pea-pod, it is not difficult to 



FIG. 790. SMALL PEA-POD, natural size, opened, two Seeds de- 

 veloped, and remains of two unfertilised Ovules ; s, Remains 

 of Style. 



recognise a great likeness to a leaf, folded along the 

 midrib, so that the lower surface is outside, and the 

 upper surface lines the cavity, which is closed by the 

 inturned edges being joined. It is now generally 

 believed that carpels are in reality leaves modified in 

 this way, and that the style is a prolongation of the 



FIG. 791. (A) CROSS SECTION OF OVARY OF ACT^A SPICATA, with 

 two anatropous Ovules on the Placentae. (B) CROSS SECTION 

 OF OVARY OF P^EOMA, showing that the Placenta; (p, p) are 

 the infolded ede;es of the Carpel. 



leaf. Thus, a single chamber is formed, and in it lie 

 all the ovules. The ovules are borne along the two 

 edges of the carpellary leaf, forming a double row, as 

 may be readily seen when a pea-pod is opened. The 

 thickened edges are called the placentae. The micro- 

 scopic structure of a pea-pod differs only in details from 



