Rosa, L. 1, L. 1
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Shrubs, usually deciduous. Stems usually with prickles. Leaves pinnate; stipules usually adnate to petiole. Flowers terminal, solitary or in corymbs, (4-)5~merous. Hypanthium urceolate, becoming coloured and fleshy in fruit; epicalyx absent; stamens and carpels numerous; styles protruding through the orifice of a disc, sometimes forming a short column; ovules 1. Fruit a pseudocarp of numerous achenes enclosed in the hypanthium.
Most species occur in scrub, woodland and hedges.
The description of leaves always refers to the best-developed leaves on the flowering stems.
The armature may include prickles, acicles (slender, needlelike structures), setae, stipitate glands and eglandular hairs.
The innumerable cultivars of Rosa to be found in European gardens (the great majority flore pleno) are mostly complex hybrids, of which the most important ancestors are 4, 6 and 14, described below, and also R. chinensis Jacq ., R. odorata var. gigantea (Collett ex Crepin) Rehder & E. H. Wilson, R. multiflora Thunb ., R. wichuraiana Crepin , all from E. Asia (though R. chinensis is not known in the wild state). Some modern garden roses, such as the 'hybrid polyanthas’, include all seven of these species in their ancestry. For the origin of garden roses see C. C. Hurst, Jour. Roy. Hort. Soc. 66: 73-82, 242-50, 282-9 (1941), and A. P. Wylie, Jour. Roy. Hort. Soc. 79: 555-71 (1954); 80: 8-24, 77-87 (1955).
In addition to these hybrids, and to the species described below, many species, mostly from E. Asia, are cultivated in gardens, and some are perhaps becoming naturalized locally. Two hybrids are cultivated on a field scale in Bulgaria and S. France for essential oil from their petals: these are R. x bifera (Poiret) Pers., Syn. PI. 2: 48 (1806) ( R. damascena auct., non Miller), which is probably a hybrid between 4 and 14 and R. x alba L. , Sp. PI. 492 (1753), whose parentage is uncertain; it is perhaps a complex hybrid between 2, 14 and a white-flowered member of Sect. Caninae .
Literature: F. Crepin, Bull. Soc. Bot. Belg. 8-21 (1869-82). H. Christ, Rosen der Schweiz. Basel. 1873. A. Deseglise, Bull. Soc. Bot. Belg. 15: 176-405, 491-602 (1876). V. Borbas, Primitiae Monographiae Rosarum Imperii Hungarici. Budapest. 1880. J. Schwertschlager, Die Rosen des siidlichen and mittleren Fran-kenjura. Miinchen. 1910. E. Willmott, The genus Rosa. London. 1910-14. G. Tackholm, Acta Horti Berg. 7: 97-381 (1922). G. A. Boulenger, Bull. Jard. Bot. Bruxelles 10 (1924); 12 (1932). A. H. Wolley-Dod, Jour. Bot. (London) 68-69 (Suppl.): 1-111 (1930-1). R. Keller, Synopsis Rosarum spontanearum Europae mediae. Zurich. 1931. C. Vicioso, Estudios sobre el Genero ‘Rosa’ en Espaha. Ed. 2. Madrid. 1964.
1 Styles connate in a column
2 Stylar column shorter than the inner stamens; styles sometimes becoming free in fruit 15. stylosa
2 Stylar column at least as long as the inner stamens; styles not becoming free in fruit 3 Inflorescence with 10-20 flowers
4 Stylar column glabrous 3. Phoenicia
4 Stylar column hairy 4. moschata 3 Flowers solitary or inflorescence with 2-7 flowers
5 Leaves coriaceous, evergreen; stylar column usually hairy
5 Leaves herbaceous, deciduous; stylar column glabrous 6 Erect shrub; stems arching; prickles very stout with very broad bases 15. stylosa
6 Trailing shrub; stems weak; prickles + slender 2. arvensis
1 Styles free 7 Sepals ± entire 8 Leaflets glabrous 9 Leaflets simply serrate
10 Stems with long prickles mixed with many short prickles and acicles 5. pimpinellifolia
10 Stems without acicles
11 Pedicels glandular-hispid 13. virginiana
11 Pedicels glabrous 9. glauca
9 Leaflets biserrate or compound-serrate 12 Petals yellow; fruit c. 10 mm, globose 6. foetida
12 Petals deep purplish-pink; fruit 15-25 mm, ovoid to elongate-pyriform, rarely globose 12. pendulina
8 Leaflets pubescent, at least beneath 13 Petals yellow 6. foetida
13 Petals white, pink or purplish-pink 14 Young stems, prickles and lower surface of the leaflets densely tomentose; leaves thick, rugose 10. rugosa
14 Young stems and prickles glabrous, the lower surface of the leaflets ± sparsely hairy; leaves not rugose 15 Pedicels glandular-hispid
16 Leaflets biserrate or compound-serrate 12. pendulina 16 Leaflets simply serrate
17 Flowering stems usually densely covered with slender prickles or acicles; sepals erect and persistent after anthesis 7. acicularis
17 Flowering stems usually without acicles; sepals patent and deciduous after anthesis 13. virginiana
15 Pedicels glabrous
18 Flowering stems usually densely covered with slender prickles or acicles; fruit ovoid, with a distinct neck below the disc 7. acicularis
18 Flowering stems without acicles; fruit usually globose 19 Stems usually with a pair of curved prickles at the nodes 8. majalis
20 Leaflets not coriaceous; petals 8-25(-30) mm 21 Leaflets glabrous or subglabrous, eglandular or very sparsely glandular
22 Leaflets bluish-green or purplish; young stems pruinose 23 Hypanthium and pedicels densely stipitate-glandular 17. montana
23 Hypanthium glabrous; pedicels rarely sparsely stipitate-glandular
24 Sepals 2-3 mm wide; prickles sparse, rather slender, curved or straight, without stout bases 9. glauca
24 Sepals 3-5 mm wide; prickles stout, curved or hooked, usually with stout bases (18-31). canina group
22 Leaflets green; young stems not pruinose 25 Pedicels glabrous (18-31). canina group
25 Pedicels stipitate-glandular
27 Leaflets subcoriaceous; prickles usually straight or slightly curved 16. jundzillii
21 Leaflets distinctly hairy or glandular or both 28 Leaflets coriaceous; petals (25-)30-45 mm 14. gallica
28 Leaflets not coriaceous; petals 8-25(-30) mm 29 Leaflets + densely viscid-glandular beneath 30 Leaflets glabrous or somewhat pubescent beneath, smelling of apples (39-47). rubiginosa group
30 Leaflets tomentose beneath, with a resinous smell (32-38). tomentosa group
29 Leaflets eglandular beneath or with glands confined to main veins
31 Prickles straight or slightly curved; leaflets always hairy and usually very tomentose, with a resinous smell (32-38). tomentosa group
31 Prickles usually curved or hooked; leaflets glabrous or pubescent, very rarely tomentose and if tomentose then prickles distinctly curved or hooked and hypanthium glabrous; leaflets usually not scented (18-31). canina group
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