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Published In: Species Plantarum 2: 1054. 1753. (1 May 1753) (Sp. Pl.) Name publication detailView in BotanicusView in Biodiversity Heritage Library

Project Name Data (Last Modified On 9/22/2017)
Acceptance : Accepted
Project Data     (Last Modified On 8/6/2009)


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1. Acer L. (maple)

Plants shrubs or more commonly small or large trees, lacking tendrils. Bark and twigs various. Winter buds ovate to elliptic-ovate, bluntly to sharply pointed at the tip, mostly with 4–12 overlapping scales. Leaves opposite, petiolate. Leaf blades variously shaped, usually palmately lobed, less commonly pinnately compound. Inflorescences terminal or lateral toward the branch tips, sometimes appearing axillary, ranging from small clusters to racemes or small panicles. Flowers actinomorphic, hypogynous, the staminate ones often perigynous. Calyces of 4 or 5(6) sepals, these sometimes fused, often colored. Corollas absent or of 4 or 5(6) free petals. Stamens 3–8 (except in pistillate flowers), usually strongly exserted, the anthers red, purple, yellow, or yellowish green. Pistil of 2 fused carpels (except in staminate flowers), usually with 2 locules, flattened at right angles to the septum. Styles 2 per flower or sometimes 1 and deeply 2-lobed, the stigmas club-shaped. Ovules usually 2 per locule. Fruits consisting of 2 samaras that are initially fused at the base but break apart at maturity and are dispersed independantly, each with a single basal seed and an obliquely terminal wing. About 115 species, widespread in temperate portions of the northern hemisphere and in mountains in the tropics.

For the treatment of the 5 species of Acer present in Missouri, please refer to Volume 2 (pp. 7–16) of the present work (Yatskievych, 2006).


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1 Leaves pinnately compound, sometimes with only 3 leaflets ... 2. A. NEGUNDO 2 Acer negundo
+ Leaves palmately lobed (2)
2 (1) Sinuses between the main leaf lobes rounded or U-shaped (3)
+ Sinuses between the main leaf lobes angled or V-shaped (4)
3 (2) Leaf blades silvery white on the undersurface, the central lobe noticeably narrowed toward the base; flowers produced before the leaves ... 4. A. SACCHARINUM 4 Acer saccharinum
+ Leaf blades lighter green on the undersurface than on the upper surface, but not silvery white, the central lobe broadest at the base or with nearly parallel sides; flowers produced during expansion of the leaves ... 5. A. SACCHARUM 5 Acer saccharum
4 (2) Leaf blades relatively deeply lobed, the lateral lobes cut 1/2–2/3 of the way to the base, the central lobe noticeably narrowed toward the base; flowers lacking petals; fruits with the wings 3.0–6.5 cm long, broadly spreading ... 4. A. SACCHARINUM 4 Acer saccharinum
+ Leaf blades relatively shallowly lobed, the lateral lobes cut 1/4–1/2 of the way to the base, the central lobe broadest at or just above the base; flowers with small petals; fruits with the wings 1.5–3.0(–4.0) cm long, narrowly spreading, sometimes appearing parallel or nearly so (5)
5 (4) Flowers produced during or after expansion of the leaves, individually short-stalked in dense, narrow panicles from branch tips, appearing pale yellowish green to yellowish white ... 1. A. GINNALA 1 Acer ginnala
+ Flowers produced before the leaves, sessile or nearly so in dense clusters from buds along the branches (the stalks elongating greatly after flowering as the fruits mature), appearing orangish red to purplish red ... 3. A. RUBRUM 3 Acer rubrum
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