ROC 



508 



ROO 



applied to the Btones with a large I nobilis; Phlox ovata; P. subulata ; P. 

 painter's brush. The spaces between ! nivalis; Vinca minor, florepleno; Cam- 

 the stones having been filled with rough panula pumila ; Gentiana verna ; Dryas 

 mortar prevents the cement from being octopetala; Digitalis lutea; Sibthorpia 

 wasted. The thickness of the latter on europsa ; Arabis alpina; Draba azoides; 

 the stones need not be more than the Premanthes purpurea; P. Muralis ; 

 eighth of an inch: it will unite the Antennaria plantaginea ; Gnaphalium 

 whole into one mass; and rock-work, ! arenanum ; Polypodium vulgare cam- 

 thus constructed, is beyond all compa- j bricum ; P. dryopteris ; Onoclea sensi- 

 rison far more natural than that made | bills ; Asplenium adiantum nigrum ; 

 in the usual way. It has none of that , Pteris caudata ; Adiantum Capillus 

 disjointed appearance which usually ac- I veneris ; Aspidium rigidum; A. Lon- 

 companies rock-woA made without ! chitis. 



cement. After a few months' exposure ! RODRIGUEZIA, Six species. Stove 

 to the weather, rock-work thus formed ' orchids. Division. Peat and wood, 

 (if skillfully made) cannot without care- { ROELLIA. Six species. Chiefly 

 ful examination be distinguished from a 'green-house evergreen shrubs. R. de- 

 ratural mass; it will soon cover all hut \currens, a half-hardy annual ; R. mu- 

 the most prominent parts. If the ce- j cosa, an herbaceous perennial. Seed, 

 ment be of a colour too light, which, or young cuttings. Sandy loam and 

 for some situations, may be the case, a i peat. 



little lamp-black, or soot, may be mixed R. ciliata is a Cape plant, and re- 

 with it. Care must, however, be taken I quires a green-house in this country, 

 that no substance which may make the ! It should be potted in light rich soil, 



cement more porous is used, otherwise 

 it will peel from the stones after a hard 

 frost. For the benefit of those who 

 are not accustomed to using cement, I 

 may mention that no more should be 

 moistened at once than can be used in 

 a short time. If the cement be good it 

 will quickly harden, and will then be in 

 a manner useless. 



" In preserving cavities in the rock 

 for plants, care should be taken that no 

 places are left in which the water may 

 lodge, or, in frosty weather, the ice, by 

 expansion, would split and peel off the 

 thin crust of cement, or lowest part of 



such as a mixture of peat, leaf-mould, 

 sand, and loam. Keep it rather dry 

 when it is not growing, but give it plenty 

 of water at other times. 



RCEPERA.. Two species. Green- 

 house evergreen shrubs. Young cut- 

 tings or seeds. Loam, peat, and sand. 

 R. aurantiaca will flower in an open 

 border. 



ROLANDRA argentea. Green-house 

 evergreen shrub. Cuttings. Loam and 

 peat. 



ROLLER. This is best made of cast- 

 iron, and may be had of four different 

 sizes, viz. with a diameter of sixteen, 



them, communicating with the soil be- , eighteen, twenty-two, or twenty-four 



neath the stones, so that the water may 

 drain off. 



" In making artificial rock for water- 

 falls, or other constructions, where the 

 cement may be constantly exposed to 

 the action of water, the best water-ce- 

 ment should be used. Any preparation 

 that does not quickly indurate under 

 water, will, in a short time, be washed 

 away, and leave nothing but the bare 

 stones." — Whateley. 



Plants suited for Rock-work are : — 

 Rhododendron ferrugineum; R. hirsu- 

 tum; Arctostaphylos Uva ursi ; Cha- 

 moeledron procumbens ; Sedum rupes- 

 tre ; S. Forsterianum ; S. popullfolium ; 



inches. The roller and water-engine, 

 where either the lawns or roads are 

 extensive, may be combined advan- 

 tageously. 



RONDELETIA. Eleven species. 

 Stove evergreen shrubs. Cuttings. 

 Loam, peat, and sand. 



ROOTS are either annual, biennial, 

 or perennial, but in all roots, and under 

 any mode of management, the fibrous 

 parts (radiculjB) are strictly annual ; they 

 decay as winter approaches, and are 

 produced with the returning vigour of 

 their parent in the spring. Hence the 

 reason that plants are transplanted with 

 most success during the season of their 



S. villosum ; S. hexangulare ; Arbutus ] decay : for, as the root almost exclu- 

 phillyres.folia ; A. pilosa ; Mahonia aqui- I sively imbibes nourishment by the 

 folium; Ramondia pyrenaica; Soldanella ] mouths of these fibres, in proportion as 

 alpina; Androsace villosa ; Crydalis i they are injured by the removal, so is 



