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Wales. Qasuarina leptoclada. — , WIL- 

 LOW. Quercus Phellos. —, YELLOW. 

 Quercus Castanea. —, WAINSCOT. 

 Quercus Cerris. 



OAK-CURRANT. A kind of gall pro- 

 duced on the cak by Cynips Quercus pe- 

 iunculi. 



OAKESIA. A North American genus 

 of Empetracece, consisting of a small de- 

 pressed branched shrub, -with narrowly 

 linear leaves in whorls of three or four, 

 and dioecious flowers in terminal heads, 

 surrounded by awned bracts. The perianth 

 is absent, but each flower is surrounded 

 by Ave or six thin scarions bracteoles ; 

 male flowers with three stamens ; females 

 with a slender three-cleft style; drupe small 

 dry, with three nuts. [J. T. S.] 



OAK-LEATHER. The common name of 

 a kind of spawn found in old oak, running 

 down the Assures, and having when re- 

 moved somewhat the appearance of white 

 kid-leather. It is figured by Sowerby 

 under the name of Xylostroma giganteum. 

 It does not appear very clearly what is its 

 perfect form, whether Dcedalea quercina or 

 some Polyporus. It is extremely common 

 in the United States, where it is some- 

 times used as a material for receiving 

 plaister, a purpose which it answers ad- 

 mirably from its pliable texture. A sub- 

 stance remarkably similar in appearance is 

 woven by certain insects on walls of 

 granaries in Brazil, the true nature of 

 which may be easily ascertained by micro- 

 scopical examination, or by burning. A 

 mycelium resembling Oak-leather also 

 occurs in Australia on different species of 

 Eucalyptus. The Oak-Ieath^r of ships suf- 

 fering from dry-rot arises from Polyporus 

 hybridus. [M. J. B.] 



OAK-LUNGS. Sticta pulmonacea. 

 OAK-SPANGLE. A kind of gall pro- 

 duced on the oak by Diplolepis lenticularis. 



OAR-WEED. A name given to the large 

 and best-known form of Laminaria digi- 

 tata, called by some authors L. Cloustoni. 



OAT. Arena sativa, —, ANIMAL. 

 Arena sterdis. — , FALSE. Arrhenathe- 

 rum, — , SEASIDE. Uniola. — , WATER. 

 An American name for Zizania aquatica. 

 — , WILD. Arena fatua. — , — of the 

 West Indies. Pharus latifolius. 



OB. A prefix signifying inversion. 

 Th; s oborate is inversely ovate ; obcordate, 

 inversely cordate ; obdurate, inversely 

 ciub-shaped, &c. 



OBCOMPRESSED. Compressed, so that 

 the two sutures of a fruit are brought 

 into contact ; flattened, back and front. 



OBELISCARIA. A genus of Composite, 

 proposed for the Rudbeckia pinnata, and 

 two other North American species which 

 have a much longer receptacle, and in 

 which the achenes' are considerably flat- 

 tened laterally, and sometimes bordered 

 by a wing on the inner edge. They would, 



however, be much better considered as a 

 section only of Rudbeckia. 



OBERONIA. A genus of nearly fifty 

 species of orchids, found principally in 

 tropical Asia. All are epiphytal plants, 

 with equitant leaves, and terminal spikes 

 of minute flowers, having free sepals, of 

 which the hind one is smaller than the 

 two others, still smaller petals, a sessile 

 immovable usually concave variously- 

 divided lip, cushioned or keeled at its base 

 and embracing the short column ; and a 

 two-celled anther containing four free 

 waxy pollen-masses. [A. S.] 



OBESIA. A name given by Haworth to 

 a group of Stapelia, now generally included 

 in that genus. 



OBIER. (Fr.) Tiburnum Opulus. 



OBIONE. The name under which cer- 

 tain species of Atriplex, as A. pedvnndata 

 and portulacoides, are sometimes separated, 

 The most obvious distinction resides in 

 the perigoneof the fruiting flowers, which 

 consists of two parts, three-toothed, free 

 only at the top, and wedge-shaped at the 

 base. The pericarp is very thin, ultimately 

 adhering to the perigone tube. [T. M.] 



OBLIQUE. Unequal-sided ; also slant- 

 ing. 



OBLONG. Elliptical, blunt at each end, 

 as the leaves of Hypericum perforatum. 



OBOLARIA. A small vernal plant be- 

 longing to the Orobanchacece, with a sim- 

 ple stem and opposite leaves, by which 

 latter character, and the fact of its being 

 terrestrial not parasitical, it differs from 

 Orobanche. O. virginica, the only species, 

 is a native of North America, especially 

 the shady woods about Lake Erie. It has 

 a small branching root, a stem from three 

 to four inches high, thick almost fleshy 

 opposite leaves, round leaf-like bracts, and 

 bell-shaped bluish-white or pale-red flow- 

 ers, which are collected into pairs or threes 

 near the summit of the stem. [C. A. J.] 



OBOVATE, or OBOVAL. Inversely 

 ovate. 



OBOVOID. Approaching the obovate 

 form. 



OBROTUND. Somewhat round. 



OBTECTO-VENOSE. Having the prin- 

 cipal and longitudinal veins held together 

 by simple cross-veins. 



OBTEGENS. Covering over anything. 



OBTUSE. Blunt, or rounded. Thus, 

 obtusely crenated is when crenatures are 

 quite round, and not at all pointed; ob- 

 tusely cut, when incisions are blunt, &c. 



OBTUSE-ANGLED. When angles are 

 rounded, as in the stem of Salvia pratensis. 



OBTUSIUSCULUS. Rather obtuse. 

 OBVERSE. The same as Ob. 

 OBVERSE-LUNATE. Inversely cres- 

 cent-shaped ; that is to say, with the 



