AN ENCYCLOPADIA 
rari 
OF. HORTICULTURE. 535 
Ourisia—continued. 
September, 1. moşjly radical, oval or oblong, unevenly but not 
deeply notched, „ bin. to 12in. Andes of Chili, 1862. See 
2 (B. M. 5335.) 
Fig. 788. OURISIA COCCINEA, 
O. Pearcei (Pearce’s).* fl. crimson, streaked with deep blood- 
red, tubular, two-lipped, several to a scape. J. ovate, coarsely 
TIEA purplish beneath. Chili, 1863. A hand i 
. M. 154.) 
ig 
OUROUPARIA. A synonym of Uncaria (which 
see). 
OUVIRANDRA (from Ouvirandrano, its native 
name, said to signify Water-yam; the roots are edible). 
ORD. Naiadaceœ. 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 1ift. deep. A compost of loam and 
Cecayed 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. 
0. (Bernier’s). jl. 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 O. fenestralis in general structure; the leaves, how- 
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. 
J. greenish- white, the flower-stem split at the top into two 
spikes. August. l. bin. to 18in. Jong, 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 Leguminose, 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 
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) 
Fic, 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 
Fic. 790. SMALL PEA-POD, natural size, opened, two Seeds de- 
. ten and remains of two unfertilised Ovules ; s, 
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 ACTHA SPICATA, with 
two anatropous Ovules on the Placente. (B) CROSS SECTION 
OF OvaRY OF Ponta, showing that the Placenta (p, p) are 
the infolded edges 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 placente. The micro- 
scopic structure of a pea-pod differs only in details from 
ee 
