AN ENCYCLOPAEDIA OF HORTICULTURE. 



309 



RIOCREUXIA (named after A. Riocreux, a cele- 

 brated botanical artist). ORD. Asclepiadece. A small 

 genus (four ? species) of slender, pubescent or glabrous, 

 greenhouse, twining sub-shrubs, confined to South Africa. 

 Calyx of five narrow segments ; corolla with an elongated 

 tube and linear lobes; corona sub-duplex, the exterior 

 of five to ten scales, the interior of five smaller ones ; 

 cymes loose, umbelliform or dichotomous; peduncles 

 simple or branched ; pedicels filiform. Leaves opposite, 

 cordate, membranous. R. torulosa, the only species in- 

 troduced, thrives in sandy loam. Plenty of pot room 

 and ample drainage must be afforded. Propagation may 

 be effected by cuttings, taken preferably in spring, and 

 inserted in sand, under a hand glass, with slight bottom 

 heat. 

 K. torulosa (somewhat twisted). Jl. pale yellow, flask-shaped, 



greenish at their ventricose base ; umbels pedunculate, lateral or 



terminal, loose-flowered. Summer. I. deeply cordate ovate. 



Roots tuberous. 1862. (Ref. B. 157.) 



RIFIDIUM. A synonym of Erianthua. 

 RIFOGONUM. See Rhipogonum. 



RITCHIEA (named in honour of Joseph Eitchie, a 

 Yorkshireman, who was killed, in 1819, when exploring 

 Central Africa). OKD. CapparidecB. A genus comprising 

 only two or three species of erect or sarmentose, climb- 

 ing, stove shrubs, natives of tropical Africa. Flowers 

 greenish, large, sweet- smelling, corymbose, long-pedicel- 

 late ; sepals four, ample, valvate ; petals four or many, 

 long-clawed, undulated, oblong, the blade imbricated; 

 torus hemispherical, fleshy. Leaves simple, or three to 

 five-foliolate ; stipules obsolete. Only one species calls 

 for mention here ; it requires treatment similar to that 

 recommended for Euadenia (which see). 



R. fragrans (fragrant). Jl. 4in. across ; sepals ovate-oblong, deep 

 green ; petals about fourteen, pale straw-colour, strap-shaped, 

 acuminate, crumpled above the middle ; stamens very numerous, 

 spreading. June. I. alternate ; leaflets three to five, as long as, 

 or longer than, the petioles, oblong or obovate-lanceolate, shortly 

 petiolulate; petioles slender, Sin. to 5in. long. h. 3ft. 1859. 

 An erect shrub. SYN. R. polypetala (B. M. 5344). 



R. polypetala (many-petaled). A synonym of R. fragrans. 



RIVEA (dedicated by Choisy to Auguste de la Eive, 

 a physiologist of Geneva). ORD. Convolvulacece. A genus 

 comprising only a couple of species of stove climbers 

 or twiners, natives of the East Indies. Flowers large, 

 on axillary, one to three-flowered peduncles ; sepals ovate 

 or oblong, obtuse; corolla salver-shaped, with a long, 

 cylindrical tube, and an angulately sub-lobed limb ; sta- 

 mens included; filaments short; bracts narrow. Leaves 

 broad beneath, and, as well as the inflorescence, often 

 woolly or silky. The species described below require 

 culture similar to Ipomoea (which see). 



R. hypocrateriformis (salver-shaped). Midnapore Creeper. 

 fl. pure white, large, expanding at sunset, and perfuming the air 

 for a considerable distance with a fragrance resembling that of 

 the finest cloves ; corolla very wide ; peduncles shorter than 

 the petioles. July. I. cordate-roundish or altogether roundish, 

 sometimes villous beneath. Western India, &c., 1799. Don 

 says this species is the prince of convolvulaceous plants. 



R. ornata (adorned). Jl., corolla white, silky without ; peduncles 

 mostly three-flowered. June. L orbicularly cordate or reniform, 

 large, clothed with cinereous tomentum beneath. Stem white ; 

 branches silky. 1824. 



RIVINA (named in honour of A. Q. Eivinus, a native 

 of Saxony, 1652-1722, for some time Professor of Botany 

 and Medicine at Leipsic). Hoop Withy. SYN. Piercea. 

 ORD. PhytolaccacecB. A genus comprising, according 

 to Bentham and Hooker, one or two species of stove, 

 erect, dichotomously - branched herbs, shrubby at base, 

 natives of tropical and sub-tropical America. Flowers 

 hermaphrodite, racemose ; perianth corolla - like, four- 

 parted ; segments obovate - oblong, obtuse, concave, 

 coloured, unchanged and erector spreading during fruc- 

 tescence ; stamens four. Fruit red, pisiform. Leaves 

 alternate, slender - stalked, ovate, ovate lanceolate, or 

 cordate-ovate, acute, obtuse, or long-acuminate, obscurely 



Rivina continued. 



crenate, membranous. Eivinas may readily be propagated 

 by seeds or cuttings, which, after being inserted during 

 spring, should be placed in heat. The plants grow freely 

 afterwards in any rich, loamy soil. When covered with 

 berries in winter time, they are exceedingly attractive. 



R. humilis (low).* Bloodberry ; Rouge Plant Jl. whitish-rose, 

 scarcely one line long, sub-reflexed ; racemes longer than the 

 leaves. January to October. Jr., berries bright scarlet, disposed 

 in racemes. I. (including the petiole) lin. to 2in. long, ovate, 

 acuminate, sub-entire, rather thick, slightly tpmentose or densely 

 pubescent. Stem shrubby ; branches, petioles, and racemes 

 slightly pubescent. A. 1ft. to 2ft. Caribbee Islands, fcc., 1699. 

 (B. M. 1781.) 



R. lajvis (smooth).* JL whitish-rose, small ; racemes lin. to 2in. 

 long. February to September, fr., berries red. I. 2iin. to 4in. 

 long, sub-cordate-ovate, acuminate, slightly crenulated, slender, 

 scarcely undulated, highly glabrous. Stem shrubby ; branches 

 glabrous, k. 7ft to 8ft West Indies, 1733. (B. M. 2333.) 



R. 1. pubescens (downy). A form with white flowers and pu- 

 bescent leaves and branches. 1699. 



RIZOA. A synonym of Gardoquia (which see). 



ROADS. Eoad-making, under a proper system, i 

 rather an expensive undertaking, particularly when the 

 requisite material is difficult to procure. It is, however,' 

 of great importance that an approach Eoad or carriage 

 drive, leading to a mansion, should be properly lined 

 out, and formed, and be afterwards kept clean and in 

 good repair. The bed should be well drained, and the 

 bottom filled, to a depth of about 1ft., with hard, porous 

 material, such as rough stones ; on this should be placed 

 about Sin. of rather finer material, such as broken 

 granite or ballast, and a similar depth of finer gravel 

 still put over the surface. In the formation of Eoads, 

 the proper levels must first be ascertained, and the full 

 depth taken out altogether, should the ground be of an un- 

 suitable description. The several depths of the different 

 sorts of material may be best indicated by pegs driven 

 in some 10ft. apart, so that their tops may be used as 

 a guide for working. 



ROAN OK ROWAN-TREE. A common name for 

 Pyrus Aucuparia. 



ROAST-BEEF PLANT. A common name for 

 Iris fostidissima. 



ROBERGIA (of Schreber). A synonym of Rourea 

 (which see). 



ROBERGIA FRUTESCENS. A synonym of 

 Connarus pubescens (which see). 



ROBERTSIA. A synonym of Sideroxylon (which 



see). 



ROBERTSONIA. Included under Saxifraga 

 (which see). 



ROBINIA (named in honour of John Robin, herbalist 

 to Henri IV. of France, and his son, Vespasian Robin, 

 who first cultivated the Locust-tree in Europe). Locust- 

 tree. ORD. Leguminosa}. A genus comprising five or 

 six species of mostly hardy, sub-glabrous, clammy, or 

 bristly trees or shrubs, natives of North America and 

 Mexico. Flowers white or rose-purple, in axillary ra- 

 cemes ; calyx teeth short and broad, the two upper ones 

 sub-connate; standard ample, reflexed, naked within; 

 wings falcate-oblong, free; keel incurved, obtuse; bracts 

 membranous, very caducous. Leaves impari - pinnate ; 

 leaflets entire, reticnlate-penniveined ; stipules bristly or 

 spiny. The species described below are all hardy and 

 deciduous, and are very handsome subjects for the orna- 

 mentation of the shrubbery. Any common soil will suit 

 them, provided it be not too wet. Propagation may be 

 best effected by layering ; the rarer kinds, however, are 

 usually increased by grafting on the commoner sorts, 

 especially R. Pseudacacia. 



R. dnbia (doubtful). A. pale rose-coloured, sweet-scented; 

 racemes loose and pendulous. June to August Pods brown, 



