OAT-GRASS ODICNEM US. 



341 



time is during Lent, and the return varies from four 

 to nine quarters per acre ; general average about five 

 quarters (forty bushels) from about five bushels per 

 acre sown. In the north, the crop is reaped and 

 bound in sheaves before it is carried to the barn. In 

 the south, oats are mown, and, when sufficiently har- 

 vested, carried to the rick or barn loose. 



OAT GRASS is the Avena prcecox of Linnaeus, a 

 common British-grass frequent on waste ground. 



OBESIA (Haworth). A genus of succulent gouty 

 plants, natives of the Cape of Good Hope. The 

 flowers are pentandrious, and the genus belongs to 

 Asclepiadccs. Both plants and flowers are curious ; 

 they require to be potted in very light soil and lime 

 rubbish, and mostly kept dry, except when flowering 

 they may be allowed \vater more freely. They are 

 propagated by cuttings, but not planted till the wound 

 gets dry, otherwise they are apt to rot. This genus 

 was separated from Stapelia. 



OBSIDIAN. This mineral is found in two very 

 distinct forms. The translucent obsidian, or Lave 

 vitreuse obsidienne of Hauy, is most frequently of a 

 black colour ; but some varieties are olive-green, and 

 exhibit a beautiful silvery or golden opalescence. 

 The island of Iceland produces the best specimens, 

 but it occurs in most parts of the world. Transparent 

 obsidian varies considerably in its colour, and consists 

 principally of silica. 



OCHNACE^E. A small natural order, contain- 

 ing four genera, viz., Ochna, Wulkeria, Gomphia, and 

 Castela. They are trees or shrubs abounding with 

 watery juices ; their stems and branches are very 

 smooth, leaves simple, alternate (in Coriaria alone 

 opposite), entire, or toothed, penninerved, and fur- 

 nished at the base with two stipules, which are deci- 

 duous, or sometimes absent. The inflorescence is 

 subracemose, the flowers regular, united, and in gene- 

 ral yellow. The calyx is formed of five sepals ; the 

 petals are equal, alternate with the sepals ; the torus 

 is turgid and discoid, bearing the carpels arranged 

 round the median style ; the stamens are five, alter- 

 nate with the petals, and protruding from the margin 

 of the disk ; the filaments are free, bearing two-celled 

 anthers, opening lengthways or by terminal pores. 

 The germen consist of from five to ten carpels 

 arranged in a whorl on the disk, with their styles 

 combined, and forming a straight thread-like column 

 that rises from the middle of the disk, and is persis- 

 tent. The fruit consists of from ten to five, or by 

 abortion fewer, carpels, which are sub-drupaceous, 

 and one seeded. 



The OchnacetE are bitter plants, and some of them 

 are esteemed as tonics, such as Walheria serrata, the 

 leaves and roots of which, when steeped or boiled in 

 milk or water, are administered as a stomachic, and 

 are said to remove nausea and arrest vomiting. 

 Gomphia hexasperma is astringent, and is found ser- 

 viceable as an application to the sores caused in 

 cattle by the punctures of insects. Gomphia Jabotapita 

 has a fruit which is eatable, but rather too astringent 

 to be agreeable ; it likewise affords a bland oil, which 

 is fit for salads and culinary purposes. The flowers 

 of this plant, as well as those of other species, are 

 very fragrant. Castela Nicholsoni is the goat-bush 

 of Antigua ; like its associates it is remarkable for its 

 bitterness, and like them might be useful as a tonic. 



There are several species of Ochna and its allies in 

 our collections : they grow well in loam and moor- 

 earth, and are propagated by cuttings. 



OCHROMA (Sweet). A genus of West Indian 

 trees, bearing monadelphous flowers, and belonging 

 to the natural order Bombaceo'. They grow freely in 

 a mixture of loam and moor-earth, and are propagated 

 by cuttings in the usual way. 



OCTOMERIA (Dr. Brown). A genus of tro- 

 pical herbaceous plants, belonging to Orchidece. In 

 our collections they are kept in pots of light sandy 

 peat-earth, placed in cold frames during summer, but 

 removed to the stove in winter. 



OCULUS CHRISTI is a species of Inula so 

 called. It is a hardy herbaceous perennial, and has 

 a place in our flower borders. It bears yellow com- 

 posite flowers. 



OCYMUM(LinnjEus) is a genus of sweet-smelling 

 herbs, belonging to Labiates. Two of the species are 

 cultivated as pot-herbs, under the name of sweet basil. 

 They are raised from seed sowed annually in spring. 



OCYPODA (Fabricius). A genus of short- 

 tailed crabs (Crustacea brachyura), having the eyes 

 large, and extending down their footstalks, instead 

 of being terminal, as in the others. The tail of the 

 males is very narrow, with the last joint elongate- 

 triangular ; that of the females is oval. The claws 

 are of nearly equal size. These crabs, as their 

 generic name implies, run with such great velocity, 

 that it is asserted that a man on horseback has 

 much difficulty in catching them ; hence the specific 

 name which was given to them by the old naturalists 

 of cavaliers (Eques}, During the day they keep in 

 their burrows, which they excavate in the sand on 

 the sea-shore. The species are chiefly tropical. The 

 type is the Cancer cursor (Linnaeus). 



ODACANTHA (Paykull). A pretty genus of 

 coleopterous insects, belonging to the family Carabidee, 

 and sub-family Brachinides, having the thorax long, 

 narrow, and subcylindrical, the elytra truncate at the 

 tips, and the tarsal joints entire. The type, and 

 only British species of the genus, is the 0. melanura 

 (Fabricius), which is found in the fens of Cambridge- 

 shire and Huntingdonshire. 



ODICNEMUS Thick-knee. A very peculiar 

 genus of Echassiers, or stilt birds, having more resem- 

 blance to the plovers than to any other family ; but 

 still so distinct from it in structure, in haunts, and in 

 manners, as to require a separate notice. Birds of 

 the allied genera, and especially this genus, were 

 most improperly classed as waders by the older sys- 

 tematists ; for, instead of wading or otherwise seeking 

 their food in the waters, they are found upon dry and 

 sandy places, and upon such only. Africa and Aus- 

 tralia are their head quarters, though some of them 

 make excursions into light sandy places in temperate 

 countries, and even pass the winter there, at least if 

 it is very mild and open. They are characteristically 

 birds of the desert, where that desert is open, and 

 they studiously avoid the cover of woods and bushes. 

 They thus form a distinct chapter in the history of 

 nature ; and their closest associates may be said to 

 be the ostriches and the bustards, the last of which 

 are found along with them in Africa ; and the emeu 

 takes the place of the ostrich in Australia, in which 

 country there is no bird, hitherto discovered at least, 

 which is properly typical of the bustards. 



That the characters of the birds are well adapted 

 to their very peculiar haunts will appear from the 

 following enumeration : the bill is longer than the 

 head, straight in its general line, and strongly made. 

 It is a little depressed at the basal part, but com- 



