3020 



ROSE 



ROYENA 



DOWNY MILDEW is caused by the fungus Peronospora sparsa. 

 It is particularly a disease of greenhouse roses, and is of somewhat 

 rare occurrence. The disease is characterized by wilting and 

 rapid killing of young leaves. 



Treatment. Dusting with sulfur is held to be effective against 



this disease. 



L. M. MASSEY. 



ROSE ACACIA: Robinia hispid-id. R.-Apple: Eugenia Jambos. 

 Rose bay: Nerium. R. Campion: Lychnis Coronaria. R., Christ- 

 inas: Hetteborus niger. R., Japanese: Kerria japonica. R. Mallow: 

 Hibiscus. Rosemary: Rosmarinus. R. of China: Hibiscus Rossin- 

 ensis. R. of Heaven: Lychnis Cceli-rosa. R. of Jericho: Anasta' 

 tica, see Resurrection Plants. R. of Sharon: Hibiscus syriacus. R., 

 Rock: Cistus and Helianthemum. R., Sun: Helianthemum, 



ROSELLE. An annual hibiscus (H. Sabdariffa, page 

 1485, Vol. Ill), cultivated in tropical and subtropical 

 regions for the acid of the immature calices and involu- 

 cels or bracteoles; known also as red sorrel and Jamaica 

 sorrel; it also yields a fiber. 



The roselle is used in the making of an acid drink and 

 also for jellies, jams, sauces, and marmalades, being a 

 good substitute for cranberry and currant in regions 

 where these fruits do not grow. It is grown somewhat 

 in the southernmost parts of the United States. The 

 culture is essentially that of the eggplant. Seeds are 

 sown in a seed-bed, and the young plants transferred to 

 rows in the field far enough apart to allow of horse- 

 tillage, and 1^ to 2 feet apart in the row. The plant 

 usually grows 4 to 5 feet high if not too highly fertilized, 

 and produces a bush of many stalks. No special tillage 

 or care is required. Before the bolls are woody or 

 stringy, they are broken off by hand. They may be 

 utilized fresh, or dried for future use. The common 

 forms of roselle are rich red and make very attractive 

 products; the yellowish forms appear not to be grown 

 in this country. The yield of one plant may be three to 

 sixteen pounds. 



ROSMARINUS (Latin, sea-dew; the plant is common 

 on the chalk hills of the south of Prance and near the 

 seacoast). Labiate. ROSEMARY. Hardy evergreen 

 shrub; a well-known garden plant, with aromatic 

 leaves used for seasoning. 



Leaves narrow, entire, with revolute margins: fls. in 

 short axillary racemes, few, approximate, opposite, 

 subsessile, bluish or white; calyx ovoid-campanulate, 

 2-lipped, posterior lip concave, minutely 3-toothed, 

 anterior 2-cut; corolla-tube exserted, limb 2-lipped, 

 posterior lip erect, emarginate or shortly 2-cut, anterior 

 spreading, 3-cut, the midlobe largest, concave, declined; 

 perfect stamens 2: nutlets smooth, ovoid-subglobose. 

 One species, Medit. region. The genus is placed near 

 Salvia, being distinguished by the calyx being only 

 shortly 2-lipped, not hairy in the throat and the con- 

 nective of the anthers continuous with the filament and 

 indicated only by a slender reflexed tooth. 



Rosmarinus offwinalis has small light blue flowers, 

 which are much sought by bees. OU of rosemary, a 

 volatile oil distilled from the leaves, is a common prep- 

 aration in drug-stores. The. leaves are also used in 

 making Hungary water. In northern herb-gardens, it 

 lasts for years if given well-drained soil and some winter 

 protection. It is recommended for hedges in southern 

 California, especially for dry and rocky places near the 

 coast. 



officinMis, Linn. ROSEMARY. OLD MAN. Shrub, 

 2^4 ft. high: Ivs. numerous, linear, with revolute mar- 

 gins: fls. axillary, in short racemes, borne in early 

 spring. V. 3:61. Var. prostratus, Hort. (R. pros- 

 tratus, Hort.), is distinguished from the type by its 

 prostrate habit. A good plant for dry positions on 



F. TRACY HUBBARD.! 



ROTHROCKIA (named for Prof. J. T. Rothrock). 

 Asdepiadacex. Perennial twining herb hardy in the 

 southwestern United States. 



Stems somewhat woody at base: Ivs. opposite, cor- 

 date-acuminate, long-petioled: infl. loose axillary 



cymes; fls. white; calyx 5-parted; corolla rotate, deeply 

 5-cleft, the lobes oblong; crown simple, inserted at the 

 junction of the corolla and stamen-tube, 5-parted: 

 follicles thickened, acuminate, smooth. Three species, 

 N. W. Mex. and Ariz. 



cordifolia, Gray. Lvs. opposite, slender-petioled, 

 cordate, acutely acuminate: fls. white or whitish, in 

 racemes; coroUa-lobes 3-4 lines long. N. W. Mex. 

 along water-courses near the borders of Ariz, and also 

 in Ariz. Cult, in S. Calif. p. TRACY HuBBARD.f 



ROTTBOELLIA (Christen Friis Rottboell, a Danish 

 botanist, 1727-1797). Graminex. Annual or perennial, 

 usually robust grasses of the tribe Andropogonea?, 

 found mostly in warmer regions of the world. The 

 species furnish some forage but they are scarcely horti- 

 cultural. Spikelets in pairs as in Andropogon, awnless, 

 arranged in cylindrical spikes, more or less embedded 

 in the axis, the first glume coriaceous and covering the 

 excavation of the rachis-joint. The genus is more 

 properly referred to Manisuris by recent authors, this 

 name being taken up on technical grounds. 



A. S. HITCHCOCK. 



ROtJPALA (probably a native name in Guiana). 

 Also spelled Ropala, Rupala, Rhopala. Protedcese. 

 Trees, smooth or ferrugineous-tomentose, suitable only 

 for the warmhouse. 



Leaves alternate, leathery, stiff, entire or dentate, 

 undivided, or those of the sterile branches (and younger 

 trees?) pinnate: fls. in axillary or terminal racemes, 

 pedicelled in pairs, perfect; perianth cylindrical, 

 slightly dilated at base, the limb scarcely broader, sub- 

 globose, oblong or elongated, finally laxly revolute; 

 ovary sessile: caps, hard, oblique, 2-valved, short- 

 stipitate. About 40 species, Trop. Amer. 



A. Hairs rust-colored. 



Pdhlii, Meisn. (R. corcovadensis, Hort.). A tree, 

 with branches clothed with rusty colored woolly 

 tomentum: Ivs. 1 ft. or more long, pinnate, with 5-8 

 pairs of Ifts. which are 3-5 in. long, on stout petiplules 

 1 in. or less long, ovate or obliquely ovate, acuminate, 

 acutely serrate: fls. J^in. long, white or yellowish, in 

 nearly sessile axillary racemes 3-5 in. long. B.M. 6095. 



AA. Hairs golden. 



aurea, Lind. According to Belg. Hort. 1866:202, this 

 species was named for the golden hairs covering the 

 upper parts of the st. and petioles. Brazil. Rare and 

 imperfectly known. 



R. Jonghei, Hort., is a plant offered by Siebrecht which does 

 not appear in botanical works. T,- -iy g ARrl AY 



F. TRACY HUBBARD. f 



ROUPELLIA: Strophanthus. 



ROYAL FERN: Osmunda regalis. R. Palm: Oreodoxa regia. 



ROYENA (named for Adrian van Royen, of Leyden; 

 died 1779). Ebenaceae. Evergreen trees or shrubs 

 suitable for the warmhouse. 



Leaves alternate: infl. axillary; fls. small, hermaphro- 

 dite; calyx deeply 5- (rarely 4-) lobed, often accrescent 

 in fr., lobes more or less pubescent or silky; corolla 

 campanulate or urceolate, 5-cleft, lobes obtuse, re- 

 flexed; stamens 10 in one rank; ovary conical, pubes- 

 cent: fr. globose, ovoid or oblong, leathery, indehiscent 

 or splitting. About 20 species, natives of Trop. and 

 S. Afr. The genus is distinguished from the 4 or 5 

 other genera of the ebony family by the fls. being 

 hermaphrodite instead of dioecious and the stamens in a 

 single series. 



Royena lutida is one of the old-tune Cape shrubs 

 formerly cultivated under glass for ornament in England 

 and lately offered in southern California. It has small 

 white flowers about J^ inch across, with five more or 

 less reflexed lobes. 



