Styrax americanus
Styrax
American snowbell, mock-orange, snowbell
snowbell, snowdrop bush, storax
petiole 2–6 mm;
blade with 5–8 secondary veins, elliptic or broadly elliptic to obovate or nearly ovate, 1.2–10 × 0.6–5.7 cm, largest blades on sterile shoots 2–5.7 cm wide, margins of at least some leaves denticulate to serrate, rarely also lobed, longest arms of abaxial hairs 0.1–0.2 mm.
blades: margins coarsely toothed, denticulate, serrate, or entire, rarely also lobed.
borne on shoots of current growing season, false-terminal or axillary racemes or panicles, (2–)3–19-flowered, sometimes solitary flowers, articulation between pedicel and flower absent.
4–10(–14) mm, longer than calyx.
calyx 2.5–4 × 2.5–4.5 mm;
corolla 11–16 mm, tube 1.5–3 mm, lobes 5(–6), imbricate or subinduplicate-valvate in bud, strongly reflexed, elliptic to narrowly elliptic, 7–14 × 1–5 mm;
filaments distinct beyond adnation to corolla.
hypanthium adnate only to proximal portion of ovary wall;
sepals (2–)4–5(–9), connate, forming tube with (2–)5(–9) minute, apical teeth;
corolla lobes 5–6(–8), imbricate or subinduplicate-valvate in bud, portion free from androecium distinct or nearly so [connate proximally];
stamens [5–]10(–16);
filaments with free portion completely distinct or connate proximally;
pistil 3-carpellate;
ovary partly inferior, proximally 3-septate;
ovules [1–2] ca. 8 per carpel, erect, bitegmic.
capsular and 3-valved, or nutlike (in S. grandifolius) [drupaceous], not winged, ellipsoid to globose;
beak indistinct.
globose, 7–9 × 7–9 mm (broader when 2–3-seeded), gray stellate-pubescent, dehiscent nearly or completely to proximal end, broadly exposing seed(s);
fruit wall 0.3–0.4 mm thick.
1(–3), completely filling fruit cavity, with 3(–6) longitudinal grooves, ellipsoid to globose;
hilum conspicuous;
seed coat thick, indurate.
-terminal inflorescences 2–5-flowered or solitary flower, 2–3.5 cm;
axillary flowers present on at least some shoots (subtending leaves often reduced).
= 8.
= 16.
Styrax americanus
Styrax
Styrax grandifolius is partly sympatric with S. americanus, and molecular data indicate that it is a close relative (P. W. Fritsch 2001). The two species are separated ecologically, with S. americanus occupying lower, moister sites (G. J. Gonsoulin 1974). Hybridization between the two is not apparent.
Some authors have recognized plants with more densely pubescent new shoots, leaves, and inflorescences and shorter pedicels as a distinct taxon, at either the specific or infraspecific level (J. K. Small 1933; A. J. Rehder 1940; G. J. Gonsoulin 1974). The most densely pubescent plants occur in the southernmost portion of the range of the species; intermediates between the two extremes are abundant. The character differences that separate the taxa are here considered taxonomically inconsequential.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Species ca. 130 (5 in the flora).
As reviewed in J. H. Langenheim (2003), many species of Styrax produce a resin exuded from wounds in the bark and wood. The southeastern Asian species S. benzoin Dryander, S. paralleloneurus Perkins, and S. tonkinensis Craib ex Hartwich are commercial sources of benzoin, a resin used medicinally as a mild antiseptic and expectorant, and in the flavor and fragrance industries. Styrax officinalis Linnaeus, native in the eastern Mediterranean region, is often anecdotally reported as a source of the resin storax (the primary source being Liquidambar orientalis Miller); well-documented bark-wounding experiments on individuals in a natural population of S. officinalis failed to produce resin (N. Zeybek 1970). To my knowledge, resin induction in any of our native species has not been attempted.
Some Styrax species are cultivated for ornament in the flora area (S. A. Spongberg 1976b; J. C. Raulston 1992). Most of the species are deciduous Asian members of series Styrax; all the native species in the flora area are cultivated to some extent as well. Two Mexican species (S. glabrescens Bentham and S. ramirezii P. W. Fritsch) have been successfully grown in warmer parts of the United States.
Nearly all Styrax species in eastern Asia serve as exclusive primary hosts for gall-forming aphids (Hormaphidinae: Cerataphidini; D. L. Stern and W. A. Foster 1996). No galls from these aphids have been observed on New World or Mediterranean Styrax.
Styrax is divided into two sections (P. W. Fritsch 1999, 2001). The predominantly north-temperate sect. Styrax is distinguished from the subtropical to tropical sect. Valvatae Gürke by the combination of the usually deciduous (versus evergreen) condition and membranous (versus subcoriaceous) corolla lobes. Two series constitute sect. Styrax. Series Cyrta (Loureiro) P. W. Fritsch is distinguished from series Styrax by the presence of lateral (as well as terminal) inflorescences on at least some shoots (versus inflorescences strictly terminal) and glandular-denticulate to glandular-serrate (versus entire) leaf margins. Three of the species in the flora (S. americanus, S. grandifolius, and S. japonicus) belong to series Cyrta; the other two (S. platanifolius and S. redivivus) belong to series Styrax.
Phylogenetic studies support the eastern Asian endemic Huodendron (four species) as the closest relative of Styrax (P. W. Fritsch et al. 2001). It differs from Styrax in its apically two- to three-toothed (versus entire) connectives, usually distally divided (versus simple) style, and a fruiting calyx that is epicarpous one-third to two-thirds the length of the fruit (versus epicarpous only slightly beyond the fruit base).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Axillary flowers absent; leaf blade margins entire, lobed, or coarsely toothed | → 2 |
1. Axillary flowers present on at least some shoots (subtending leaves often reduced); at least some leaf blade margins denticulate to serrate, rarely also lobed | → 3 |
2. Capsules 7-10 mm, grayish white stellate-pubescent; pedicels 1.3-2.3 times as long as calyx. | S. platanifolius |
2. Capsules 11-15 mm, tawny or fulvous stellate-pubescent; pedicels 0.5-1.4 times as long as calyx. | S. redivivus |
3. Pedicels 15-50 mm. | S. japonicus |
3. Pedicels 4-10(-14) mm | → 4 |
4. Calyces 2.5-4 mm; corolla tubes 1.5-3 mm; false-terminal racemes 2-3.5 cm; largest leaf blades on sterile shoots 2-5.7 cm wide; longest arms of abaxial leaf hairs 0.1-0.2 mm; fruits capsular, dehiscent nearly or completely to proximal end, broadly exposing seed(s). | S. americanus |
4. Calyces 4-6 mm; corolla tubes 3-5 mm; false-terminal racemes 3-11.5 cm; largest leaf blades on sterile shoots 5-20 cm wide; longest arms of abaxial leaf hairs 0.2-0.6 mm; fruits nutlike, indehiscent or at most with 1-3 narrow longitudinal fissures, barely exposing seed(s). | S. grandifolius |
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