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ARTICLES PAGE | Hawaii Manual: Part 1 - Part 2 - Part 3 |
Bishop Museum Special Publication 83
5. HIBISCADELPHUS Rock Hau kuahiwi
Shrubs or trees with smooth, greyish bark and prominent petiole scars on young branches, glabrate to stellate puberulent. Leaf blades broadly ovate to subreniform in outline, sometimes 3-angled, 5-angled, or 7-angled to shallowly lobed, both surfaces glabrous or pubescent, margins entire or shallowly to deeply crenate or dentate, base cordate, petioles usually 1/3 or more the length of blades, stipules obscure, subulate to triangular, caducous. Flowers borne near the ends of branches, 1(2) in the leaf axils, pedicels not articulate; involucral bracts 4-9, filiform to triangular or spatulate, connate basally into a narrow disk or ca. 1/3 their length; calyx tubular to saccate, 5-lobed but often opening by 2-3 clefts, persistent in fruit or circumscissilly dehiscent toward base before capsule maturity; corolla usually zygomorphic, green, yellowish green, or magenta, curved and narrowly convolute with the 2 lower petals shorter and usually spreading or reflexed apically, densely stellate pubescent on lower surface and often on upper surface near apex, usually conspicuously veined; staminal column exserted or exposed apically by the spreading lower petals, antheriferous in upper 1/3-1/2 below the 5-dentate apex; ovary 5-celled, ovules (2)3 per cell; style branches 5, erect; stigmas terminal, capitate or discoid. Fruit a woody or chartaceous, ovoid to oblong-ovoid, densely pubescent, 5-valved, loculicidally dehiscent capsule, mesocarp reticulate-veined, endocarp separating from it as 5 or 10 chartaceous segments. Seeds reniform, densely matted or loose, grayish to yellowish silky tomentose. [Bishop & Herbst, 1973; Carr & Baker, 1977; Degener & Degener, 1977a; Forbes, 1920; Hobdy, 1984; Radlkofer & Rock, 1911]
Hibiscadelphus comprises 6 species endemic to the Hawaiian Islands. The name means brother of Hibiscus and alludes to the close relationship of the 2 genera.
KEY TO THE SPECIES OF HIBISCADELPHUS
Involucral bracts connote ca. 1/3 their length;
mesocarp weakly developed and usually adnate to
Page 878 of the Manual MALVACEAE
Involucral bracts connate slightly at base; reticulate
mesocarp strongly developed; endocarp
Presumably small trees. Leaf blades broadly oblong-ovate, 3-8.5 cm long, upper surface sparsely pubescent, lower surface densely pubescent, especially in axils of major veins, 3-angled or 5-angled or lobed, margins irregularly crenate, base deeply cordate with a closed sinus, petioles 1-5 cm long. Flowers solitary, pedicels ca. 2 cm long in flower, up to 4 cm long in fruit; involucral bracts 6, connate slightly at base, linear-oblong to spatulate, 9-10 mm long, 1-5.3 mm wide; calyx tubular-campanulate, ca. 1.2 cm long, apparently deciduous; corolla moderately curved, ca. 3.3 cm long. Capsules woody, slightly obovoid, apiculate, 2.5-3 cm long, mesocarp strongly developed, reticulate, endocarp segments 10. Seeds ca. 6 mm long, yellowish lanate. Apparently now extinct, collected only once, before 1868, probably in mesic forest, at Kawaihae, Hawai'i (Forbes, 1920; Degener, 1937c).
Trees up to 6 m tall with rounded crown, trunk ca. 16 cm in diameter. Leaf blades ovate to broadly ovate, 5-14 cm long, unlobed, upper surface essentially glabrous, lower surface sparsely stellulate pubescent and stellate-tufted in the lower vein axils, margins entire to 7-11-dentate, base openly cordate, petioles 1.5-5 cm long flowers solitary, pedicels 2-3.5 cm long; involucral bracts 4-5, green, connate slightly at base, spatulate, 20-30 mm long, 3-7 mm wide, with a prominent midrib, glabrate; calyx dark purple, curved-saccate, 4.2-4.9 cm long, irregularly 1-3-cleft, deciduous; corolla dark purple, inconspicuously veined, 5-6.5 cm long. Capsules woody, subglobose, 5-angled, beaked, ca. 2.3-2.7 cm long and in diameter, mesocarp strongly developed, reticulate, endocarp segments 10. Seeds 5-7 mm long, matted grayish white pubescent. Formerly known from a single tree, discovered in 1981 and now dead, on a windward, dry slope of Puhielelu Ridge, 750 m, Lana'i.
Seeds were harvested by Hobdy from this plant on several occasions; however, none germinated.
Among the specimens taken from the only individual is one [Hobdy 1041.5 (coll. R Connally), BISH] with the calyx and corolla in the size range of Hibiscadelphus wilderianus. Its involucral bracts, however, are filiform, ca. 1 mm wide and ca. 12 mm long, being shorter and narrower than those of H. wilderianus and within the range of H. x puakuahiwi (see H. giffardianus).
Shrubs or small trees up to 5 m tall with grayish, rounded crown, trunk 5-8 cm in diameter. Leaf blades broadly ovate, 4-10 cm long, upper surface sparsely pubescent,
HIBISCADELPHUS Page 879 of the Manual
lower surface more densely so but without conspicuous tufting in the vein axils, margins broadly and sometimes irregularly dentate, base shallowly cordate, petioles 1.5-5 cm long, stipules 1-2 mm long. Flowers solitary, erect, pedicels 1-3 cm long; involucral bracts 7-9, 12-16 mm long, connate ca. 1/3 their length, limbs narrowly triangular, 1.5-2.3 mm wide at base; calyx tubular, 1.3-2 cm long, lobes triangular, 0.3-0.5 cm long; corolla bright green, becoming dull reddish, 3-4 cm long. Capsules chartaceous, ovoid, ca. 2.5 cm long, 1.5 cm in diameter, mesocarp weakly developed and usually adnate to exocarp, endocarp segments 5, boat-like. Seeds 2 per cell, reniform, ca. 5 mm long, sparsely yellowish brown pubescent. [2n = 40*.] Known from a population of 10 individuals, discovered in 1972, in remnant dry forest, ca. 350 m, on a bluff above Koai'e Stream, Waimea Canyon, Kaua'i. This species has been federally listed as endangered (Herbst, 1986f). - Plate 123.
A total of about 16 individuals was reported from subsequent trips to this area, but their present status since Hurricane 'Iwa in 1982 is unknown (D. Herbst, pers. comm.).
Trees up to 7 m or more tall, trunk up to 30 cm in diameter. Leaf blades orbicular to subreniform in outline, 10-25(-30) cm long, usually 3-angled or 5(7)-angled, both surfaces pubescent in the vein angles, base deeply cordate with overlapping sinuses, petioles often approaching blades in length, stipules 1-2 mm long. Flowers solitary, pedicels 1.5-3(-4) cm long; involucral bracts 5-7, connate slightly at base, filiform, stiffly spreading or reflexed, 18-35 mm long, up to 1.1 mm wide; calyx saccate, 2.7-3.7(-4.5) cm long, 2-3-cleft; corolla grayish green externally, dark magenta within, (5-)6-7 cm long. Capsules woody, oblong-ovoid, 4-5 cm long, 2-2.5 cm in diameter, mesocarp strongly developed, reticulate, endocarp segments 10. Seeds 7-10 mm long, grayish white tomentose. [2n = 40*.] A single tree was found in 1911 in mesic forest at Kipukapuaulu, 1,310 m, on the eastern slopes of Mauna Loa, Hawai'i; apparently now extinct in the wild.
Hibiscadelphus giffardianus. persists in cultivation, principally at Kipukapuaulu, Hawai'i Volcanoes National Park (Degener, 1932d). Hybrids between H. giffardianus and H. hualalaiensis, described as H. x puakuahiwi K. Baker & S. Alien, were once common at Kipukaki, but were recently destroyed. For discussions of this situation refer to Baker and Alien (1976, 1977) and Degener and Degener (1977a). Presumably hybrids exist elsewhere in cultivation.
Trees 5-7 m tall, trunk up to 30 cm in diameter. Leaf blades ovate to orbicular, 10-15 cm long, sometimes 3-5-angled, margins entire to slightly undulate-dentate, base deeply cordate but usually with an open sinus, petioles 4-10 cm long, stipules 1.5-2 mm long. Flowers 1-2 in the leaf axils, pedicels 1.5-3(-14) cm long; involucral braces usually 5, connate slightly at base, tooth-like, 0.5-2(-3) mm long; calyx tubular to subsaccate, 1.5-2.5(-3) cm long, 2-3-cleft or 5-lobed; corolla greenish yellow externally, yellowish green fading to purplish within, 2-5(-5.5) cm long. Capsules woody, oblong-ovoid to ellipsoid-ovoid, grooved, apiculate, 2.2-3 cm long, mesocarp strongly developed, reticulate, endocarp segments 10. Seeds reniform, up to 7 mm long, densely grayish white lanate. [2n = 40*.] Very rare, formerly occurring in dry to mesic forest, lava flows of Hualalai and forest of Waihou, North Kona, Hawai'i; as of 1977, 2-3 plants were still extant in the wild. Otherwise it is known only from cultivation (D. Herbst, pers. comm.). - Plate 123.
Trees up to 5 m tall. Leaf blades broadly ovate to transversely ovate in outline, 7-11 cm long, sometimes 3-angled, both surfaces sparsely stellate pubescent, tufted in the principal vein axils on lower surface, mar-
HIBISCADELPHUS / HIBISCUS Page 881 of the Manual
gins subentire to broadly undulate-crenate, petioles 5-7 cm long, stipules ca. 1.2 mm long. Flowers solitary, pedicels 1-3 cm long; involucral bracts 5-6, connate only at base, linear to ligulate or subspatulate, 11-18 mm long, 1.1-2 mm wide; calyx tubular-saccate, 2.3-2.5 cm long, 5-lobed or irregularly cleft; corolla apparently yellowish green, 3.5-5 cm long. Capsules woody, broadly ellipsoid, invaginate apically, ca. 3.5 cm long, mesocarp strongly developed, reticulate, endocarp segments 10. Seeds not known. A single tree was found in 1910 at 800 m, on the dry forest lava fields of Auwahi, southern slopes of Haleakala, Maui; apparently now extinct, but see note under H. crucibracteatus.
6. HIBISCUS L., nom. cons. Aloalo
Subshrubs to trees or sometimes herbs, variously pubescent with simple, stellate, and glandular hairs, rarely glabrous, occasionally spiny. Leaves simple, petiolate, stipulate, blades unlobed or palmately lobed or divided. Flowers solitary, cymosely clustered in the leaf axils, or in racemes, panicles, or corymbs by reduction of upper leaves, pedicels usually articulate; involucral bracts 4-20, distinct or connate basally or adnate to calyx at base; calyx campanulate to tubular or suburceolate, 5-lobed or 5-parted, often accrescent in fruit, veins obscure or prominent, sometimes with a gland on midrib of each lobe; corolla white, yellow, orange, red, or purple, often maroon-spotted at base, rotate to campanulate or tubular, lower surface usually densely pubescent; staminal column included or exserted, antheriferous for most of its length or only below the 5-toothed apex; ovary 5-celled or rarely appearing 10-celled by a vertical partition, ovules 3 or more per cell; style 5-branched, each branch terminated by an expanded stigma. Fruit a loculicidally dehiscent capsule, exocarp and endocarp sometimes separating at maturity. Seeds angular-reniform or rounded-reniform, glabrous or pubescent. [Bates, 1965, in Wagner, Herbst & Sohmer, 1989; Bergman, 1932; Caum, 1930; Degener & Degener, 1977b; Forbes, 1912; Gray, 1854a; Heller, 1897; Hochreutiner, 1900; Hooker& Arnott, 1832; Leveille, 191lb; Menzel, Fryxell & Wilson, 1983; Niimoto, 1966; Roe, 1961; St. John, 1972a; Skottsberg, 1944a; Walpers, 1843b]
As generally recognized, Hibiscus is a diverse and certainly polyphyletic assemblage of perhaps 200 species, primarily of tropical and subtropical regions of the world.
The species have in common relatively few characters, including a 5-celled capsular fruit and distinct style branches. The native species are the result of 4 independent colonization events, 2 for the endemic species (one for the white-flowered and red-flowered species and one for H. brackenridgei) and one each for the indigenous species. Name derived from hibiscos, the Greek name for mallow.
Leveille (1911b) described Hibiscus fauriei as native to 0'ahu, based on a collection made by Faurie in Honolulu. The collection actually represents H. schizopetalus (Mast.) J. D. Hook., an ornamental that has been cultivated in Hawai'i since around 1900. Hibiscus rosa-sinensis L., Chinese hibiscus or red hibiscus, a glabrate shrub with petals reddish to dark red with a darker red spot at the base (or in cultivated forms the corollas vary from single to double and from white through shades of red, yellow, and orange), is one of the most common ornamentals in Hawai'i. It may occasionally persist around abandoned homesites, although it does not appear to be truly naturalized. Hybrid derivatives of crosses between this species and the native white-flowered and red-flowered Hibiscus are difficult to identify.
KEY TO THE SPECIES OF HIBISCUS
Staminal column antheriferous from near base to apex,
usually shorter than petals (2).
Page 882 of the Manual MALVACEAE
enclosing the bud, foliaceous, 10-100(-150) mm long,
deciduous leaving an annular scar (3).
Shrubs or small trees up to 8(-10) m tall, glabrous to glabrate or sometimes young stems, petioles, and calyces copiously yellowish stellate pubescent. Leaf blades coriaceous, ovate-elliptic to broadly ovate, usually 4-15(-30) cm long, 2-11(-25) cm wide, upper surface glabrous or glabrate, lower surface glabrate to densely pubescent, margins entire or dentate throughout or near apex, apex acute to subacuminate, base obtuse to subcordate or cuneate, petioles usually less than 1/2 the length of blades, stipules subulate to filiform, 5-10 mm long, caducous. Flowers weakly fragrant, solitary, borne near the ends of the branches, pedicels stout, 1.5-6(-9) cm long, articulate; involucral bracts 5-7, reflexed to erect, linear-lanceolate to narrowly oblong, 5-15(-25) mm long, 1-2 mm wide; calyx tubular, (1.5-)2-3(-3.4) cm long, lobes deltate-acute, 3-10 mm long; petals flaring, white, occasionally with a pink tinge on abaxial side, sometimes aging pinkish, (5-)6-11(-13) cm long from point of insertion, adnate basally to the staminal column into a tube 1-3(-4) cm long; staminal column exserted, pinkish to dark red, rarely white,
HIBISCUS Page 883 of the Manual
8-19 cm long; filaments arising in upper 1/3-1/2 of staminal column, red or white, spreading, 0.8-3 cm long. Capsules chartaceous, obovoid-apiculate, ca. 1,7-2.5 cm long, glabrous, endocarp smooth, shiny, exocarp reticulate-veined. Seeds ca. 4 mm long, yellowish brown tomentose. [2n = 80*, 84*.] Occurring in primarily mesic to wet forest, 300-800 m, Wai'anae and Ko'olau mountains, O'ahu, and Wailau Valley, Moloka'i. - Plate 123.
White-flowered, indigenous populations of Hibiscus, treated here as 2 modally distinct species, collectively comprise a complex of morphological forms in which character intergradation is extensive, although differences between individual populations or plants may be pronounced. Many variants have been or are in cultivation, and some have been hybridized with H. rosa-sinensis (Wilcox & Holt, 1913; Bates, 1965). Distinctions drawn between H. arnottianus on O'ahu and H. waimeae on Kaua'i and their respective subspecies largely recognize modal differences between populations on the 2 islands. The species are maintained pending detailed population studies.
Three subspecies of Hibiscus arnottianus are recognized: subsp. arnottianus [incl. H. arnottianus f. parviflorus, H. waimeae var. hookeri] with young stems, leaves, pedicels, and calyces glabrate, leaves 4-10 cm long, involucral bracts reflexed, 5-8(-10) mm long, calyx 1.5-2.8 cm long, and petals (5-)6-8(-10) cm long from point of insertion (Wai'anae Mountains and eastern end of Ko'olau Mountains from Wahiawa to Niu Valley, 120-790 m, Oahu); subsp. immaculatus, which differs from subsp. arnottianus in having usually deeply crenate leaves, caudate calyx teeth, white staminal column, and capsules enclosed by the calyx (extremely rare, Wailau, Waihanau, and Papalaua valleys, Moloka'i, perhaps reduced to about a dozen individuals); and subsp. punaluuensis, a robust variant with young stems, leaves, pedicels, and calyces moderately coarsely pubescent, leaves 10-20(-30) cm long, involucral bracts apparently appressed to the calyx, 10-25 mm long, calyx 2-3.4 cm long, and petals (7-)8-11(-13) cm long from point of insertion (Ko'olau Mountains from Kaipapau to Waiahole, 200-700 m, O'ahu). A single collection (Forbes 1000, BISH) from the western flanks of Konahuanui, Oahu, is somewhat intermediate between subsp. arnottianus and subsp. punaluuensis.
Sprawling to erect shrubs 1-3 m tall, or small trees up to 5(-10) m tall; young branches glabrate to densely stellate pubescent, often with scattered, reddish to yellowish, spreading, simple, spinescent, pustular-based hairs. Leaf blades orbicular in outline, 5-15 cm long and wide, shallowly to usually deeply 3-lobed, 5-lobed, or 7-lobed, lobes ovate to obovate and sometimes overlapping, acute, coarsely serrate or even secondarily lobed, midvein on lower surface with or without a basal gland, both surfaces glabrate to puberulent, base truncate to cordate, petioles slender, usually more than 1/2 the length of blades, stipules filiform, 5-15 mm long, early deciduous, leaving an elliptic scar. Flowers solitary or few in short terminal racemes, pedicels stout, not articulate, 0.5-1.7 cm long; involucral bracts 7-10, sometimes spreading, adnate basally to calyx, subulate to linear-lanceolate, 8-22(-30) mm long, 1-2.5 mm wide at base, channeled or plane and sometimes secretory apically, with or without hispid, pustular-based, simple or 2-3-branched hairs; calyx reddish to yellowish, 1.5-4 cm long, somewhat larger in fruit, lobed to middle or more deeply, usually hispid with simple to few-branched hairs, with or without a raised, elongate gland on midrib of each triangular lobe; petals yellow, usually with a maroon spot at base, drying greenish or purple, spreading, 3.5-8 cm long; staminal column exserted, closely antheriferous in upper 3/4 or nearly to base. Capsules subglobose to ovoid, beaked, 1.1-2 cm long, densely villous-hispid. Seeds angulate-reniform, up to 4.5 mm long, puberulent. [2n = 144*, ca. 140*.] Rare and local in dry forest and shrubland, 130-800 m, on all of the main islands
Page 884 of the Manual MALVACEAE
except Ni'ihau and Kaho'olawe. This species was reportedly collected on Kaho'olawe by Remy. - Plate 123.
Hibiscus brackenridgei is closely related to the widespread H. divaricatus Jacq. and may not be specifically distinct from it. Hibiscus brackenridgei varies morphologically from island to island, but population series seem to fall into 2 principal morphological types, treated as subspecies: subsp. brackenridgei [incl. H. brackenridgei var. molokaiana], a sprawling to erect shrub or small tree with calyx 1.5-2.5 cm long, involucral bracts 1/2 as long to as long as the calyx, and petals with or without basal maroon spotting, 3.5-5(-6) cm long, occurring in dry forest and shrubland, near sea level up to 370 m, on Moloka'i, Lana'i, Maui, and Hawai'i; and subsp. mokuleianus, a tree with calyx 2.5-4 cm long, involucral bracts 18-25 mm long, and maroon-spotted petals 6-8 cm long, occurring in a similar habitat, at Lihu'e and reportedly Olokele Canyon, Kaua'i, and.in the Wai'anae Mountains between Kawaihapai and Pu'upane, 120-240 m, O'ahu. The pubescence of subsp. brackenridgei varies from stellate to hirsute with simple hairs, and the calyx midvein usually bears an obscure, bordered gland. Plants of subsp. mokuleianus are spiny-hirsute with simple, pustular-based hairs. The midvein gland, if present at all, is hidden by the dense, pustular bases of the hairs.
Perennial herbs or shrubs 1-3 m tall; young stems green, stellate tomentose, later glabrate. Leaf blades basically orbicular in outline, 3-10(-12) cm long and wide, unlobed or obscurely to distinctly 3(-5)-lobed, both surfaces stellate pubescent, margins serrate to crenate-dentate, apex acute, base truncate to subcordate, petioles usually more than 1/2 the length of blades, stipules subulate to filiform, 5-15 mm long, persistent. Flowers solitary, pedicels usually shorter than subtending petiole, not articulate; involucral bracts 5, connate at base, usually broadest above middle and abruptly narrowed to a caudate tip, up to 20(-30) mm long; calyx 1.7-2 cm long, winged in bud, lobed to near middle, lobes cordate-ovate, long-acuminate, midrib raised but eglandular; petals flaring, sulfur-yellow, brownish maroon to maroon basally, 4-8 cm long; staminal column included, 1.5-2 cm long, antheriferous for most of its length; style branches erect; stigmas maroon, appearing coherent. Capsules ellipsoid, 1.8-2.5 cm long, the valves scarious, aristate, densely stellulate pubescent. Seeds up to 3 mm long, tomentose. [2n = 40, 80*.] Widely distributed in tropical and southern Africa and on Madagascar and the Masearene Islands; in Hawai'i cultivated and naturalized in low elevation dry areas on Kaua'i. First collected in 1919 (Rock 16038, BISH); the specimen probably was a cultivated plant (Caum,
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