Acer

Family: Aceraceae
Genus: Acer
Species:

A. capillipes, A. ginnala, A. griseum A.laevigatum, A. maxomowiczianum, A. monspessulanum, A. grosseri, A. japonicum, A. palmatum, A. tataricum, A. zoeschense, A. acuminatolobum, A. amplum, A. argutum, A. barbatum, A. barbinerve, A. buergerianum, A. caesium, A. calcaratum, A. campbellii, A. campestre, A. capillipes, A. cappadocicum,
A. carpinifolium, A. caudatum, A. circinatum, A. cissifolium,
A. coriaceifolium, A. crataegifolium, A. davidii, A. diabolicum,
A. discolor, A. distylum, A. elegantulum , A. fabri, A. labellatum, A. forrestii, A. ginnala, A. giraldii, A. glabrum, A. granatense, A. grandidentatum, A. griseum A. grosseri, A. heldreichii, A. henryi, A. hersii, A. hyrcanum, A. japonicum,
A. laevigatum, A. laurinum, A. laxiflorum, A. leucoderme, A. lobelii, A. longipes, A. macrophyllum, A. mandshuricum, A. maximowiczianum, A. maximowiczii, A. micranthum, A. miyabei, A. mono, A. monspessulanum, A. negundo, A. nigrum, A. nikoense, A. oblongum, A. obtusifolium, A. oliverianum, A. opalus, A. palmatum, A. paxii, A. pectinatum,
A. pensylvanicum, A. pentaphyllum, A. platanoides, A. pseudoplatanus, A. pseudosieboldianum, A. pycnanthum,
A. robustum, A. rotundilobum, A. rubescens, A. rubrum,
A. rufinerve, A. saccharinum, A. saccharum, A. sempervirens,
A. shirasawanum, A. sieboldianum, A. sikkimense, A. sinense, A. skutchii, A. spicatum, A. stachyophyllum (A. tetramerum), A. sterculiaceum (A. villosum), A. syriacum (A. obtusifolium), A. tataricum, A. tegmentosum, A. tonkinense,
A. trautvetteri, A. triflorum, A. truncatum, A. tschonoski (A.komarovii), A. tsinglingensis, A. turkestanicum, A. ukurunduense, A. velutinum, A. wilsonii, A. yangbiense (newly discovered in Yunnan, China), A. zoeschense

Morphology:

Maples are mostly trees growing to 10-40 metres (30-130 ft) in height. Others are shrubs less than 10 metres tall with a number of small trunks originating at ground level. Most species are deciduous, but a few in southern Asia and the Mediterranean region are evergreen.

Maples are distinguished by opposite leaf arrangement. The leaves in most species are palmately veined and lobed, with 3-9 veins each leading to a lobe, one of which is in the middle. A small number of species differ in having palmate compound, pinnate compound, pinnate veined or unlobed leaves.

Several species, including the Paperbark Maple (Acer griseum), Manchurian Maple (Acer mandshuricum), Nikko Maple (Acer maximowiczianum), and Three-flowered Maple (Acer triflorum), have trifoliate leaves. One species, Manitoba Maple (Acer negundo), has pinnately compound leaves that may be simply trifoliate or may have five, seven, or rarely nine leaflets. One maple, the Hornbeam Maple (Acer carpinifolium), has pinnately-veined simple leaves that resemble those of hornbeam.


Red Maple (Acer rubrum) flowersThe flowers are regular, pentamerous, and borne in racemes, corymbs, or umbels. They have five sepals, five petals about 1 to 6 mm long, 12 stamens about 6-10 mm long in two rings of six, and two pistils or a pistil with two styles. The ovary is superior and has two carpels, whose wings elongate the flowers, making it easy to tell which flowers are female. Maples flower in late winter or early spring, in most species with or just after the leaves appear, but in some before them.

Maple flowers are green, yellow, orange or red. Though individually small, the effect of an entire tree in flower can be striking in several species. Some maples are an early spring source of pollen and nectar for bees.

The distinctive fruit are called samaras or "maple keys". These seeds occur in distinctive pairs each containing one seed enclosed in a "nutlet' attached to a flattened wing of fibrous, papery tissue. They are shaped to spin as they fall and to carry the seeds a considerable distance on the wind. Seed maturation is usually in a few weeks to six months of flowering, with seed dispersal shortly after maturity. Most species require stratification in order to germinate, and some seeds can remain dormant in the soil for several years before germinating.

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