The World Flora Online

Shrubs or trees, terrestrial or epiphytic, with various hairs, and/or with peltate scales or glabrous, indumentum sometimes detersile (the hairs tangled and coming away as a layer). Leaves evergreen, deciduous or semideciduous, alternate, sometimes clustered at stem apex; margin entire, very rarely crenulate, abaxial indumentum sometimes with a pellicle (a thin skinlike layer on the surface). Inflorescence a raceme or corymb, mostly terminal, sometimes lateral, few- to many-flowered, sometimes reduced to a single flower. Calyx persistent, 5–8-lobed, sometimes reduced to a rim, lobes minute and triangular to large and conspicuous. Corolla funnelform, campanulate, tubular, rotate or hypocrateriform, regular or slightly zygomorphic, 5(–8)-lobed, lobes imbricate in bud. Stamens 5–10(–27), inserted at base of corolla, usually declinate; filaments linear to filiform, glabrous or pilose towards base; anthers without appendages, opening by terminal or oblique pores. Disk usually thick, 5–10(–14)-lobed. Ovary 5(–18)-locular, with hairs and/or scales, rarely glabrous. Style straight or declinate to deflexed, persistent; stigma capitate-discoid, crenate to lobed. Capsule cylindrical, coniform, or ovoid, sometimes curved, dehiscent from top, septicidal; valves thick or thin, straight or twisted. Seeds very numerous, minute, fusiform, always winged, or both ends with appendages or thread-like tails.

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6. Rhododendron L.

Por J.L. Luteyn.

Arbustos o árboles; indumento de pelos unicelulares, multicelulares, glandulares y eglandulares, y escamas. Hojas alternas a seudoverticiladas, perennes o deciduas, pecioladas o subsésiles, aplanadas a longitudinalmente rizadas, coriáceas o cartáceas, pinnatinervias, los márgenes enteros o rara vez ciliado-serrulados. Inflorescencias terminales o axilares, peruladas, umbeliformes o corimbosas, a veces solitarias; pedicelos continuos con el cáliz; brácteas y bractéolas deciduas. Flores 5-meras, sin aroma, la, estivación imbricada; lobos del cáliz libres, generalmente 5(-10); corola simpétala, (4-)5-8(-10)-lobada, rotácea a campanulada, o infundibuliforme, a veces tubular, generalmente zigomorfa, decidua; estambres 5-10(-20); filamentos desiguales, pubescentes o glabros; anteras sin apéndices, el tejido de desintegración ausente, dehiscentes por poros terminales; polen con hilos de viscina; ovario súpero, 5(-20)-locular. Frutos secos en cápsulas septicidas, generalmente ovoides a oblongas; semillas numerosas, diminutas, aladas a fusiformes. Aprox. 900 spp. Zonas templadas, la mayoría en Asia y Norteamérica. 1 especie cultivada en zonas Neotropicales.

Bibliografía: Clemants, S.E. Fl. Neotrop. 66: 131-132 (1995).

La única especie en Mesoamérica es Rhododendron simsii .

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RHODODENDRON L.

Rhododendron simsii Planch., Fl. Serres Jard. Eur. 9: 78. 1854.

Arbustos 1 m de alto, con todas las partes vegetativas cubiertas con tricomas aciculares escamiformes y tricomas cortos frecuentemente piloso-glandulares. Hojas alternas o pseudoverticiladas, membranáceas, elíptico-lanceoladas a oblanceoladas, 2.5–4.5 cm de largo y 1–1.5 cm de ancho, ápice agudo u obtuso y mucronado, base aguda, margen ciliado; pecíolos 3–5 mm de largo. Inflorescencias corimbos o racimos terminales, pocas flores; cáliz 8–10 mm de largo, irregularmente lobado o hendido, cubierto con tricomas glandulares; corola asimétrica, hipocrateriforme, ampliamente patente distalmente, ca 4.5–5 cm de largo y de ancho, glabra, blanca con puntos rojo-morados; estambres 5, más o menos desiguales, inclinados, anteras ca 2 mm de largo, sin espolones; ovario densamente fasciculado hirsutos. Cápsula septicida no vista.

Cultivada, Matagalpa; 1270 m; fl dic; Stevens 22576. Un género con casi 900 especies distribuidas en las regiones templadas mayormente en Asia y Norteamérica; sólo esta especie es cultivada en América tropical.

S.E. Clemants. Rhododendron Linnaeus. Ericaceae Part II. The superior-ovaried genera. Fl. Neotrop. 66: 131–132. 1995.

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Subshrubs, shrubs, or trees, (rhizomatous or not). Stems erect (and/or creeping, prostrate in R. groenlandicum, R. lapponicum, R. tomentosum); twigs hairy or glabrous, (older twigs without peglike projections). Leaves persistent or deciduous, alternate; petiole present; blade coriaceous to membranous, (base cuneate, rounded, or obtuse), margins entire, (sometimes ciliate, plane to revolute, abaxial surface 1/3+ visible except sometimes in bud, surfaces hairy and/or scaled, midvein hairy or not, adaxial surface sometimes impressed; venation usually brochidodromous). ( Winter buds usually large, with imbricate scales; floral buds usually larger than vegetative buds.) Inflorescences terminal (axillary in R. albiflorum, short, corymbiform or rounded racemes (fasciculate racemes in R. canadense, R. lapponicum; fasciculate in R. albiflorum), 3-35-flowered (1-2-flowered in R. albiflorum); perulae brownish, scalelike, dry. ( Pedicels horizontal to erect (recurved); bracteoles 2, brownish, scalelike, basal.) Flowers bisexual, weakly bilaterally symmetric (radially symmetric in R. columbianum, R. groenlandicum, R. tomentosum, scented or not); sepals 5[-9], slightly connate; petals 5[-9], strongly to only slightly connate (sometimes nearly distinct), corolla deciduous, rotate to campanulate or funnelform; stamens 5-12[-20], included to long-exserted; (filaments usually unequal, usually unicellular-hairy, glabrous in R. vaseyi, glabrous or proximally unicellular-hairy in R. groenlandicum, R. lapponicum); anthers without awns, dehiscent by terminal pores; ovary 5[-18]-locular; style inserted in slight depression at ovary apex or smoothly intergrading, (usually curved, long, slender); stigma capitate. Fruits capsular, elongate, usually ovoid to cylindric, dehiscence usually basipetally septicidal (acropetally septicidal in R. columbianum, R. groenlandicum, R. tomentosum). Seeds (10-)100+, flattened-ellipsoidal to fusiform, often tailed, ± winged; testa smooth. x = 13.

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Cal 5-lobed, much shorter than the cor; cor campanulate to funnelform, conspicuous, regularly or commonly irregularly 5-lobed; stamens mostly 5 or 10, with elongate filaments and short anthers with 2 terminal pores; ovary superior, 5-locular; style elongate; capsule septicidal; shrubs or trees with alternate, deciduous or evergreen lvs and showy fls in terminal racemes or umbel-like clusters from scaly buds. Our spp. 2n=26, except as noted. (Azalea) 850, mainly N. Hemisphere.

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Terrestrial or epiphytic, evergreen or deciduous, shrubs or trees or occasionally subshrubs; indumentum extremely variable including unicellular, uniseriate, multiseriate-multicellaular glandular and eglandular hairs, and scales, persistent or not. Leaves alternate to pseudoverticillate, exstipulate, petiolate or subsessile; blades simple, flat to longitudinally curled, coriaceous or chartaceous, marginally entire or rarely ciliate-serrulate. Buds with several to many imbricate scales. Inflorescence terminal or less commonly axillary, perulate, umbelliform or corymbose, sometimes solitary; pedicels not articulating with the calyx; bracts and bracteoles brown and deciduous. Flowers: calyx lobes free, usually 5(-10), often somewhat reduced; corolla sympetalous, (4-)5-8 (-10)-lobed, rotate to campanulate, or funnelform, sometimes tubular, usually zygomorphic, deciduous, white to yellow, pink, purple, or deep red; stamens 5-10(-20), filaments usually unequal, pubescent or glabrous; anthers unappendaged, dehiscing by an ovate terminal pore; ovary 5(-20)-locular, superior; style slender, curved; stigma capitate. Fruit a dry septicidal capsule, usually ovoid to oblong; seeds numerous, minute, flat, and more or less winged to fusiform.

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SELECTED REFERENCES Chamberlain, D. F. 1982. A revision of Rhododendron II. Subgenus Hymenanthes. Notes Roy. Bot. Gard. Edinburgh 39: 209-486. Chamberlain, D. F. et al. 1996. The Genus Rhododendron: Its Classification and Synonymy. Oxford. Chamberlain, D. F. and S. J. Rae. 1990. A revision of Rhododendron IV. Subgenus Tsutsusi. Edinburgh J. Bot. 47: 89-200. Cullen, J. 1980. A revision of Rhododendron. 1. Subgenus Rhododendron sections Rhododendron and Pogonanthum. Notes Roy. Bot. Gard. Edinburgh 39: 1-207. Goetsch, L., A. J. Eckert, and B. D. Hall. 2005. The molecular systematics of Rhododendron (Ericaceae): A phylogeny based upon RPB2 gene sequences. Syst. Bot. 30: 616-626. Harmaja, H. 1991. Taxonomic notes on Rhododendron subsection Ledum (Ledum, Ericaceae), with a key to its species. Ann. Bot. Fenn. 28: 171-173. Judd, W. S. and K. A. Kron. 1995. A revision of Rhododendron VI. Subgenus Pentanthera (sections Sciadorhodion, Rhodora, and Viscidula). Edinburgh J. Bot. 52: 1-54. Kron, K. A. 1993. A revision of Rhododendron section Pentanthera. Edinburgh J. Bot. 50: 249-364. Kurashige, Y. et al. 2001. Sectional relationships in the genus Rhododendron (Ericaceae): Evidence from matK and trnK intron sequences. Pl. Syst. Evol. 228: 1-14. Philipson, W. R. and M. N. Philipson. 1986. A revision of Rhododendron III. Subgenera Azaleastrum, Mumeazalea, Candidastrum and Therorhodion. Notes Roy. Bot. Gard. Edinburgh 44: 1-23. Sleumer, H. 1980. A system of the genus Rhododendron L. In: J. L. Luteyn and M. E. O’Brien, eds. 1980. Contributions toward a Classification of Rhododendron: Proceedings, International Rhododendron Conference...May 15-17, 1978.... Bronx. Pp. 1-18.

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