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Published In: The Gardeners Dictionary...Abridged...fourth edition vol. 1. 1754. (28 Jan 1754) (Gard. Dict. Abr. (ed. 4)) Name publication detail

Project Name Data (Last Modified On 8/11/2017)
Acceptance : Accepted

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1. Alnus Mill. (alder)

(Furlow, 1979)

Plants shrubs or trees, sometimes forming thickets. Young growth (twigs, leaves, and inflorescences) with a sticky or resinous coating. Twigs 1.5–2.0 mm thick, dark purplish brown, usually hairy, the pith more or less triangular in cross-section. Buds stalked, with 2 or 3 scales. Leaf blades elliptic, rhombic, or very broadly obovate to almost circular, the tip broadly or bluntly pointed to shallowly notched, the undersurface green, hairy (at least along the veins), but not or scarcely felty to the touch, the lateral veins 6–11 on each side of the midrib and sometimes branched. Stamens 4, undivided. Styles persistent at fruiting. Fruits samaras with 2 small lateral wings, brown, arranged in conelike aggregates of mostly 50–120 fruits. Bracts fused into a relatively flat structure, unlobed or very shallowly 5-lobed woody scales that overlap and more or less conceal the fruits, the scales persistent on the axis after the fruits are dispersed. About 25 species, North America to South America, Europe, Asia.

Alders are very important ecologically for their ability to fix nitrogen, that is, to transform inert gaseous nitrogen from the atmosphere into nitrates and other compounds useful to living things. Like other nitrogen-fixing plants, the chemical reactions occur in root nodules that contain symbiotic microorganismsin the case of Alnus, bacteria (actinomycetes) in the genus Frankia. The leaves and bark are rich in tannins, so alders have been used for tanning leather; in traditional medicine they have been used to treat various kinds of infections and inflammations, especially of the skin (Moerman, 1998). The foliage and bark also yield dyes; depending on the parts of the plant used and the method of preparing and applying the dye, they can be yellow, red, or black. The conelike infructescences of some species have been marketed in handicrafts and jewelry as miniature pinecone substitutes.


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1 1. Plants trees 4–15 m tall; bark medium gray, smooth on younger branches but fissured with age; leaf blades usually nearly circular, occasionally very broadly obovate, the tip shallowly notched, truncate, or occasionally broadly rounded, the margins coarsely toothed and sometimes also with small, shallow lobes ... 1. A. GLUTINOSA

Alnus glutinosa
2 1. Plants shrubs or small trees 1.5–3.0(–6.0) m tall; bark light gray, smooth; leaf blades elliptic to rhombic, the tip broadly or bluntly pointed to rounded, the margins finely toothed, not lobed ... 2. A. SERRULATA Alnus serrulata
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