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桦木属  

2017-05-07 03:17:15|  分类: 校园·教育 |  标签: |举报 |字号 订阅

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桦木属 Betula, 樺木科 Betulaceae, 殼斗目 Fagales= 山毛櫸目, 豆类植物 Fabids蔷薇类植物 Rosids真双子叶植物 Eudicots

The simple leaves are alternate, singly or doubly serrate, feather-veined, petiolate and stipulate.  They often appear in pairs, but these pairs are really borne on spur-like, two-leaved, lateral branchlets.

The bark of all birches is marked with long, horizontal lenticels raised pores in the stem of a woody plant that allows gas exchange between the atmosphere and the internal tissues.

The flowers are monoecious; 花 单性,雌雄同株

柔荑花序成熟后不会木质化并碎裂,以释放种子; 

果实是小的翅果 samara  


Birch trees (Betula spp.) are a popular choice for the home landscaper. Their distinctive bark and beautiful leaves make them prized shade and ornamental trees. 


Paper Birch (Betula papyrifera) (美國)

Habitat: In rich or sandy soils;.

 60-70 feet high;

Leaves Egg-shaped; finely, doubly toothed; 

Bark: White; peeling and papery; 

The fruit  a samara  releasing a million seeds.


Water Birch (Betula occidentalis)

To 25 feet tall.

Bark: Smooth; dark bronze.

Fruit: A winged strobile (=cone) about an inch long.


Betula platyphylla 白桦= 桦木 (中國)

白色纸状树皮,三角状卵形叶;花 单性,雌雄同株,柔荑花序;圆柱形果序单生下垂.

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桦木属 - henrythomas - henrythomas 的博客

 Paper Birch (Betula papyrifera) (美國) (dead tree)


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楊屬 Populus, 楊柳科 Salicaceae, 金虎尾目 Malpighiales

雌雄异株,没有花瓣,有环状花盘苞片种子小,具冠毛

The fruit is a two- to four-valved dehiscent capsule, green to reddish-brown, mature in midsummer, containing numerous minute light brown seeds surrounded by tufts of long, soft, white hairs which aid wind dispersa


White Poplar (Populus alba)

Along the sides of roads and near home sites; 

Up to 50 feet high;

Leaves: Up to 4 inches long; bluntly pointed; very broadly toothed; dark green above; silvery white and fuzzy below; 

Bark: Smooth and grayish or white at first; at maturity deeply furrowed and blackish.

Flowers: On catkins 柔荑花序 (spike 穗状花序) ; fruits tiny, attached to cottony hairs.


Big-Toothed Aspen (Populus grandidentata)

30-70 feet high; 

Bark: Thin; more or less smooth; whitish or yellowish; typically becoming furrowed

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