and oblique, short stamens inserted in 

 the middle of the tube, and a short slender 

 style ending in a round head. The only 

 species is O. serpentinum, a native of the 

 Ease Indies, a climbing shrub with leaves 

 in whorls. The name is from the Greek 

 words for ' serpent 'and ' wood,' in allusiou 

 to the twisted root and stems. [G. D.] 



OPHIRA, or OPHIRIA. A synonym of 

 GrubUa, applied by recent authors to one 

 of the sections of that genus. 



OPHIURIS. A genus of grasses belong- 

 ing to the tribe Rottboellece. The inflores- 

 cence is in solitary or compound spikes ; 

 spikelets one or two-flowered, the inferior 

 sterile, the superior fertile ; glumes two, 

 the lowest thick and leathery, five to seven- 

 nerved, the uerves often obsolete ; the upper 

 thin and paper-like, two to three-nerved ; 

 stamens three; styles two. Steudel de- 

 scribes nine species, which are either tro- 

 pical or subtropical. [D. MJ 



OPHRY8. A genus of terrestrial orchids, 

 with the habit of Orchis, but the flowers 

 have no spur, and the lip is usually very 

 convex resembling more or less the body 

 of a bee or other insect. Hence the names 

 of Bee-orchis, Spider-orchis, &c, under 

 which they are popularly known. There 

 are a considerable number of species in the 

 countries bordering on the Mediterranean, 

 and they are often found there in great 

 abundance in spring and the early part of 

 summer. In Britain we have but few, of 

 which the principal are the 0. apifera, or 

 Common Bee-orchis with a broad very con- 

 vex lip of a rich velvety brown, and 0. mus- 

 cife-ra or Fly-orchis with an oblong purplish 

 brown lip with pale marks in the centre. 

 Both grow in dry pastures chiefly in the 

 south-eastern counties. 



OPIUM. The inspissated juice of Papa- 

 ver somniferum. — , LETTUCE. Lactu- 

 carium, the juice of Lactuca sativa and 

 L. virosa. 



OPLISMEXUS. A genus of grasses be- 

 longing to the tribe Panicece, now included 

 in Panicum. Only one of the species is 

 British, namely, 0. Orusgalli, better known 

 as Panicum or Echinochloa Cms galli, which 

 occurs sparingly on the southern coast of 

 England. [D. M.] 



OPOBALSAMUM. An oleo-resin obtain- 

 ed from Balsamodendron gileadensis, and 

 B. Opobalsamum. 



OPOCHALA. Pentaclefhra macrophylla, 

 an oil-yielding plant of W. Tropical Africa. 



OPOIDIA. Dr. Lindley has described a 

 Persian herbaceous plant under this name, 

 and considers it to form a genus of Umbel- 

 Uferce. It has a tall stout erect stem, with 

 decurrent pinnate leaves ; the general um- 

 bels unsurrounded by bracts, the partial 

 ones having an involucel of many bracts ; 

 the calyx obscurely five-toothed, and the 

 petals yellowish. Fruit cylindrical or oval, 

 with three ridges, and having a large oil- 

 channel beneath each furrow, and a smaller 



one beneath each ridge. O.galbanifera w„_ 

 so named under the idea that it produced 

 the foetid gum-resin known as galbanum, 

 but this seems open to doubt. [M. T. MJ 



OPOPANAX. Dioscorides and other 

 Greek writers mention a medicinal plant 

 under this name, which is used by botanists 

 to designate a genus of Umbelliferce, re- 

 presented by a single species, O. Cliiro- 

 nium, a plant six or seven feet in height, 

 resembling the parsnip, and a native of 

 the South of Europe. Its leaves are bi- 

 pinnate, with unequal heart-shaped seg- 

 ments and crenated margins; and the 

 flowers are yellow, in compound umbels, 

 with both partial and general involucres, i 

 an undeveloped calyx-limb, and roundish 

 petals, with the point bent inwards. The 

 fruit is thin, flattened from back to front, 

 each half with three thread-like ridges, 

 and three oil-channels in each furrow, with , 

 six others on the surface that adjoins the 

 other half-fruit. The plant yields a milky 

 juice, which dries into agum-resin, having 

 similar properties to those possessed by 

 ammoniaoum, but is now scarcely used. 

 The plant is to be met with here and 

 there in botanic gardens, but is of no 

 ornamental value. [M. T. M.] 



OPORANTHCS. A genus of Amaryllida- 

 cece, founded on the Amaryllis lutea, avery 

 pretty dwarf autumn-flowering bulbous 

 plant of the South of Europe. It has round- 

 ish bulbs, hiemal lorate leaves, and one- 

 flowered scapes, supporting the pure yellow 

 flowers, which are crocus-like in shape but 

 larger. It is distinguished by its solid 

 scape, by the short funnel-shaped tube 

 of its cupless regular perianth, and by its 

 filaments being inserted equally within 

 the mouth of the perianth tube. [T. Mj 



OPORIXIA. Leontodon. 



OPPOSITE. Placed on opposite sides of 

 some other body or thing and on the same 

 plane. Thus, when leaves are opposite, 

 they are on opposite sides of the stem ; 

 when petals are opposite, they are on op- 

 posite sides of the flower ; and so on. 



OPPOSITIFOLITJS. Opposite a leaf, that 

 is to say, growing on the side of a stem 

 opposite to that on whicli a leaf grows ; 

 also applied to leaves opposite each other. 



OPUNTIACE^E. The same as Cactacece 

 (which see). One of the divisions of this 

 order receives the name of Opuntidce. 



OPUNTIA. The Prickly Pears form a 

 most extensive genus, consisting of up- 

 wards of a hundred and fifty species, con- 

 fined to the American continent, and, like 

 the rest of the order, inhabiting hot dry 

 places. They abound chiefly in Mexico and 

 California in the northern, and in Brazil, 

 Chili, and Peru in the southern hemisphere. 

 All the species are more or less fleshy, es- 

 pecially while young ; but as they get old 

 most of them form a short round woody 

 trunk, and the older branches also become 

 hardened. They are erect or decumbent, 

 and seldom grow higher than eight or ten 



