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ALDER

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Originally appearing in Volume V01, Page 533 of the 1911 Encyclopedia Britannica.
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ALDER , a genus of See also:

plants (Alnus) belonging to the See also:order Betulaceae, the best-known of which is the See also:common alder (A. glutinosa). The genus comprises a few See also:species of shrubs_ or trees, seldom reaching a large See also:size, distributed through the See also:North Temperate See also:zone, and in the New See also:World passing along the See also:Andes southwards to See also:Chile. The See also:British species A. glutinosa is confined to the Old World. This See also:tree thrives best in moist soils, has a shrubby See also:appearance, and grows under favourable circumstances to a height of 40 or 50 ft. It is characterized by its See also:short-stalked roundish leaves, becoming See also:wedge-shaped at the See also:base and with a slightly toothed margin. When See also:young they are somewhat glutinous, whence the specific name, becoming later a dark See also:olive See also:green. As with other plants growing near See also:water it keeps its leaves longer than do trees in drier situations, and the glossy green foliage lasting after other trees have put on the red or See also:brown of autumn renders it valuable for landscape effect. The stout cylindrical male' catkins are pendulous, red-dish in See also:colour and 2 to 4 in. See also:long; the See also:female are smaller, less than an See also:inch in length and reddish-brown in colour, suggesting young See also:fir-cones. When the small winged fruits have been scattered the ripe, woody, blackish cones remain, often lasting through the See also:winter. The alder is readily propagated by seeds, but throws up See also:root-suckers abundantly. It is important as See also:coppice-See also:wood on marshy ground. The wood is soft, See also:white when first cut and turning to See also:pale red; the knots are beautifully mottled.

Under water the wood is very durable, and it is there-fore used for piles. The supports of the Rialto at See also:

Venice, and many buildings at See also:Amsterdam, are of alder-wood. See also:Furniture is sometimes made from the wood, and it supplies excellent See also:charcoal for See also:gunpowder. The bark is astringent; it is used for tanning and See also:dyeing. ALDER-See also:FLY, the name given to neuropterous See also:insects of the See also:family Sialidae, related to the See also:ant-lions, with long filamentous antennae and four large wings, of which the anterior pair is rather longer than the posterior. The See also:females See also:lay a vast number of eggs upon grass stems near water. The larvae are aquatic,active, armed with strong See also:sharp mandibles, and breathe by means of seven pairs of abdominal branchial filaments. When full-sized they leave the water and spend a quiescent pupal See also:stage on the See also:land before See also:metamorphosis into the sexually mature See also:insect. Sialis lutaria is a well-known British example. In See also:America there are two genera, Corydalis and Chauliodes, which are remarkable for their relatively gigantic size and for the immense length and sabre-like shape of the mandibles.

End of Article: ALDER

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