Styrax americanus
Styracaceae
American snowbell, mock-orange, snowbell
snowbell family, storax family
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.
alternate, simple;
stipules absent;
petiole present;
blade margins serrate or entire, rarely also lobed.
false-terminal and/or axillary racemes or panicles, sometimes solitary flowers.
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.
bisexual [plants gynodioecious];
perianth and androecium perigynous to epigynous;
hypanthium adnate to ovary wall at various levels;
sepals (2–)4–5(–9) [absent], distinct or connate, sometimes forming tube with or without minute apical teeth;
petals 4–5(–8), connate proximally;
stamens usually 2(–4) times [equaling] number of corolla lobes, adnate to corolla at base only or to 1/2 length of corolla, uniseriate in appearance;
anthers dehiscent by longitudinal slits;
pistils 1, 2–4[–5]-carpellate;
ovary partly or completely inferior, proximally 2–4[–5]-septate, 1-locular by distal attenuation of septa;
placentation axile [near basal];
ovules anatropous, uni- or bitegmic, tenuinucellate;
styles 1, simple [3-parted];
stigmas 1, terminal, truncate or minutely 2–4[–5]-lobed.
capsular, dehiscence loculicidal, or nutlike (dry and indehiscent), sometimes winged, [drupaceous].
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.
1–4[–ca. 50], brown, ellipsoid to globose or fusiform [flat, winged];
embryo straight or slightly curved;
endosperm copious, cellular, oily.
-terminal inflorescences 2–5-flowered or solitary flower, 2–3.5 cm;
axillary flowers present on at least some shoots (subtending leaves often reduced).
= 16.
Styrax americanus
Styracaceae
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.)
Genera 11, species ca. 160 (2 genera, 7 species in the flora).
Species of Halesia and Styrax are sometimes cultivated for ornament, and species of Alniphyllum, Melliodendron, Pterostyrax, Rehderodendron, and Sinojackia have been successfully grown in the United States.
About 80% of the species of Styracaceae belong to Styrax; the next largest genera in the family are Rehderodendron and Sinojackia, with five and six species, respectively. All genera are endemic to eastern and/or southeastern Asia with the exception of the two in the flora.
The Styracaceae have been shown to be monophyletic on the basis of morphological and DNA sequence evidence (P. W. Fritsch et al. 2001). Studies with DNA sequence data place Styracaceae within order Ericales (in the sense of Angiosperm Phylogeny Group 2003; C. M. Morton et al. 1996; A. A. Anderberg et al. 2002) as sister to Diapensiaceae, and Styracaceae + Diapensiaceae are sister to Symplocaceae (J. Schönenberger et al. 2005). The South American genus Pamphilia is now included within Styrax (B. Wallnöfer 1997; Fritsch 1999, 2001).
The fossil record of the Styracaceae extends back to the early Eocene (B. H. Tiffney 1985).
In the present treatment, calyx dimensions include the hypanthium, whereas those of the corolla and stamens do not. Leaf dimensions are those of the larger examples on each specimen except where noted.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Winter buds without scales; pith continuous; inflorescences borne on shoots of current growing season; fertile shoots of current growing season with fully developed leaves; articulation between pedicels and flowers absent; corolla lobes 5-6(-8); ovaries partly inferior; fruits not winged. | Styrax |
1. Winter buds with scales; pith chambered; inflorescences borne on shoots of previous growing season; fertile shoots of current growing season without fully developed leaves (rarely fully developed); articulation between pedicels and flowers present; corolla lobes 4; ovaries completely inferior; fruits winged. | Halesia |
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