named in honour of Ritchie the African 

 traveller. The leaves are ternate, and the 

 flowers in terminal racemes. The calyx 

 has four concave sepals ; the corolla an 

 equal number of stalked petals, placed on 

 the margin of a hemispherical fleshy recep- 

 tacle ; and the stamens are twelve to six- 

 teen, inserted with the petals ; the ovary 

 is placed on the end of a long stalk, and is 

 capped by a sessile orhiculate stigma. R. 

 fragrans is a handsome stove-climber with 

 white flowers. [M. T. MJ 



RTVACHE LAITEUX, R. DES MARAIS, 

 or R. SAUVAGE. (Fr.) Peucedanum syl- 

 vestre. 



RIVEA. A genus of Convolvulacece 

 found in the tropics of both hemispheres, 

 and composed of about a dozen species, all 

 of which are shrubby climbers of great 

 beauty, generally having cordate leaves and 

 being more or less covered with hair. The 

 calyx has five sepals ; the corolla is tubular 

 or funnel-shaped, and often purple; the 

 style is solitary, and bears at the apex a 

 capitate or almost two-lobed stigma; the 

 ovary is four- celled, with one ovule in 

 each cell ; and the fruit is succulent and 

 indehiscent, in which respect the genus 

 differs from most other members of the 

 Convolvulus tribe. Several species are 

 cultivated in our gardens. [B. S.] 



RIVER- WEED. An American name for 

 Podostemon. 



RIVINA. This genus comprises about 

 eight or ten species, all American, except 

 one which is doubtfully Asiatic. It is 

 characterised by having a somewhat co- 

 rolla-like four-parted calyx, with equal ulti- 

 mately erect or rarely reflexed segments, 

 and mostly only four stamens, and by its 

 berries at length becoming dry and juice- 

 less. The species are undershrubs, with 

 usually erect stems, alternate stalked mi- 

 nutely stipulate leaves, either quite entire 

 or obsoletely crenulate, and terminal and 

 lateral racemes of small flowers. 



R. humilis, a common plant in hothouses, 

 has beautiful racemes of little bright 

 scarlet berries, which before drying up 

 contain a very fine scarlet juice, the colour 

 of which, however, is very evanescent. It 

 is a native of the West Indies and of the 

 continent of America from Texas to Bra- 

 zil. [A. SJ 



RIVULARIA. A genus of green-spored 

 Algce belonging to the natural order 

 Oscillatoriei, in which the gelatinous ele- 

 ment is so predominant that the plant 

 presents itself in masses of a more or less 

 definite form. These are attached to rocks, 

 plants, &c, or float loosely on the surface 

 of the water, and have been sometimes 

 confounded with Tremellce. The structure 

 is very beautiful. Each branchlet is obtuse 

 at the base, and much attenuated upwards 

 till it becomes a mere colourless hair-like 

 point. The outer coat is very thick and 

 gelatinous, and at the base of each is a 

 large connecting cell, which was diverted 

 from the mother-thread or branch, and 



from which it was originally developed. 

 The mass of threads, therefore, exhibits 

 very curious mode of branching, which it 

 is at first very difficult to comprehend. The 

 species grow both in fresh and salt-water, 

 and where there is much carbonate of 

 lime in solution the frond becomes some- 

 times very hard and crystalline. [M. J B.] 



RIWASCH. An Eastern name tor Rheum 



Ribes. 



RIZ. (Fr.) Oryza. — D> ALLEMAGNE. 



Sordeum Zeocriton. 



ROASTBEEF-PLANT Iris fcetidissima. 



ROBIN DECHTRE. (Fr.) Lychnis Flos- 

 cuculi. 



ROBINET. (Fr.) Lychnis dioica. 



ROBINIA. A great number of species 

 have at different times been placed in this 

 genus, but it is now restricted to a few 

 North American trees and shrubs, one of 

 which, commonly called Acacia in this coun- 

 try, is a well-known object of ornament. All 

 the species have deciduous pinnate leaves, 

 frequently with prickly spines at their 

 bases in place of stipules, each leaf con- 

 sisting of from five to ten pairs of leaflets 

 and an odd terminal one, the leaflets being 

 furnished with stipels (secondary stipules) 

 at their bases, and usually of an egg- 

 shaped or oblong form. Their flowers, 

 produced in conspicuous usually pendulous 

 racemes from the leaf-axils, vary from 

 white to rose-coloured, and are succeeded 

 by narrow flat thin-shelled pods containing 

 several seeds, and having the seed-bearing 

 edge thicker than the other parts. They 

 have a short five-toothed slightly two-lip- 

 ped calyx ; a pea-like eorolla, with the large 

 rounded upper petal turned back in the 

 fully expanded flowers ; one free and nine 

 united stamens ; and a slender downy 

 style. 



R. Pseud-Acacia, the Common or False 

 Acacia, or North American Locust, is a 

 large tree from fifty to eighty feet high, 

 with smooth naked young branches, and 

 loose slender racemes of sweet-smelling 

 white flowers, producing smooth pods. It 

 is a native of the United States, from 

 Pennsylvania southward to Carolina. R. 

 viscosa— so called because its young 

 branches, instead of being smooth like 

 those of the last, are covered with a sticky 

 substance— is a much smaller tree, and dif- 

 fers also in having nearly scentless flowers 

 tinged with rose-colour, and crowded 

 together in shorter racemes, and in the 

 pods being covered with glandular hairs. 

 It is a native of the Southern States of 

 North America. R. hispida, the Rose 

 Acacia, has large deep rose-coloured scent- 

 less flowers in loose racemes ; besides 

 which it differs from the above two species 

 in size, seldom growing higher than six or 

 eight feet, and in its young branches and 

 leafstalks being thickly clothed with 

 bristles. It also is a native of the Southern 

 States of America. 



The North American Locust or False 

 Acacia has had the most extravagant 



