Ob'IiISAte— Neoeasary, essential. 



Ob'i^oate Parasite — An organism to which 

 a parasitic life is indispensable for the 

 attainment of its full development. 



Oblis'ulate, Obligula'tus — When the 

 corolla of a ligulate floret (in Compositae) 

 is extended on the inner instead of the 

 outer side of a capitulum. 



Obhqce', Obli'quus— When the midrib of 

 a plane leaf being nearly horizontal, 

 but pointing somewhat towards the 

 ground, the limb itself is more or less 

 inclined to the horizon, owing to a 

 twist in the petiole or in the base of the 

 limb. Also, when a plane leaf is so 

 divided by tlie midrib that the divisions 

 on each side are slightly unequal, as 

 the baae of many Bucalypt leaves. 



Ob'long, Oblong'us— Of an elliptical shape, 

 where the major and minor axis bear a 

 proportion to each other of about four 

 to one. 



Obova'lis— Used as a synonym for " Obo- 

 vate."" 



Obo'vate, Obova'tus — When the point of* 

 attachment is at the narrow end of the 

 ovate form. 



OBRI^'GENS — When the ringent corolla of 

 a floret (in CompositEe) has the interior 

 lip composed of one-fifth, and the 

 posterior of four-fifths, of the whole. 



Ob'scubus— Of a dark or dingy colour. 



Obsteuo'tds — Where hairs, ciliae, or other 

 appendages partially close the throat 

 of a tubular corolla. 



Obsob'dlate, Obsubula'tus— Very narrow 

 pointed at the base, but gradually 

 widening a little towards the apex. 



Obsuidea'lis {Ob, over against, sutura, a 

 suture.) — Applied to the suture of a 

 pericarp. 



Obtura'tor— A small body which accom- 

 panies the poUenic mosses of Orehideae 

 and Asclepiadeae, closing the opening of 

 the anther. 



Obtu'bus — Blunt. OBTnsius'cuLUS — 

 Somewhat blunt. 



Obvalla'tus — When consecutive pairs of 

 opposite leaves are arranged at small 

 angles of divergence from each other, 

 and not in a brachiate manner, where 

 the angle is a right angle. 



Obvek'sus — When the point of the radicle, 

 in the seed, approaches the hilum. 



Obvoluti'ous — When the margins of leaves 

 or petals, in the bud state, are mutually 

 enrolled one within the other. More 

 especially applied to two plicate leaves, 

 which, in vernation, have each one 

 margin embraced by the folding of the 

 other leaf. 



Ocean'idus— Belonging to the Ocean. 

 Synonym for " Hydrophyton.' 



Ocoulta'tus— Hidden. 



Ooblla'tus, Oobllate— Spotted in a 

 manner somewhat resembling the pupil 

 and iris of an eye. One spot of colour 

 within another spot, as the pink-eyed 

 variety of Vinca rosea, var. ocdlata, an 

 abundant weed in Qaeensland. 



Oohka'ceus — The colour of yellow-ochre ; 

 yellow, with a little grey. 



Ooh'eea— See " Ocrea." 



OoHBOLEu'cns— Of a pale yellow, with a 

 faint tinge of dingy yellow. 



OoHEOPHLO'iA— Yellow bark, as Eucalyp- 

 tus ochrophloia, the Paroo Yellow 

 jacket. 



O'OHEA — A membranous sheath at the base 

 - of some leaves, which clasps the stem. 

 (See Polyyonum orientale, a tall showy 

 weed of swampy land.) 



Oct or Ooto— Eight in composition. Thus : 

 Octagt'nia, flowers with eight pistils 

 or eight free styles; Ootan'deia, 

 flowers with eight stanlens ; Ootogt- 

 nia, synoiiym for " Ootagynia ;" 

 Octo'nus, eight together; Ootosib- 

 MONUS, with eight free stamens. 



Oo'ULUS— The first appearance of a bud, 

 especially the bud on a tuber. Also a 

 small depression on the summit of 

 fruits, as the Apple and Pear. 



Odes, Oides— A termination denoting simi- 

 larity, resemblance. 



Odora'tus — Possessing any decided odour 

 though more generally restricted to 

 such as are sweet, as the Reseda odorata, 

 Mignonette. 



Offioina'lis — Applied to those plants 

 which are or may have been considered 

 useful in medicine or the arts, as Ver- 

 bena officinalis, the Holy Herb. 



Olea'ginous, Oleaginub — Succulent and 

 oily ; also like oil. 



O'lens— Strong-scented, whether agree- 

 able or nauseous. 



Oleea'ceods (From olus, a pot herb) — Escu- 

 lent, eatable, as the Pig-'weed, Port-u- 

 laea olerueea. 



Ol'igos — Few, or in small number ; in com- 

 position, "01igo"and "Olig.' 



Oli'gos (In Greek compounds, a small 

 number) — It is generally used in con- 

 trast with many (poly), when no speci- 

 fic number is employed, as in the defi- 

 nition of things the number of which 

 is small, but variable ; thus oligocar- 

 pous is applied to sori, in which the 

 spore-cases are few in number ; oligor- 

 rhiza where the roots are few in num- 

 ber, as in the little Duck-weed, Lemna 

 oUgorrhiza. 



Oliva'ceus— Of an olive-green colour ; 

 orange and grey. (See Sarcochilus 

 oHvaceus.) Oliv.e formis, Olivifoe'mis 

 — Shaped like an olive", ellipsoidal. 

 (See fruit of OhrysophyllumoHvmforme.) 



Omople'phttum— Synonym for a plant 

 with a monadelphous flower, because 

 the stamens are blended together into 

 one bundle. 



OmphaIjO'dium (From omphalos, the navel, 

 and eidos, a resemblance. ) — The mark 

 left in the hilum by the passage of the 

 vessels of the raphe. 



Ontog'ent — Development of an individual. 



Oogamy — Conjugation of two gametes of 

 dissimilar form. 



Oogonium — A kind of ovarian sack contain- 

 ing spores which, when liberated, are 

 cdlled oospores. 



OospoEE — Spores produced in an ovarian 

 sac. 



O'PAQUB, Opacus— When the surface is dull 

 or not at all shining. 



