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SMOOTH ALDER. 

 Alnus rugosa, (Du Roi) Sprengel. 



GENUS DESCRIPTION The Alders comprise about 2,1 known species, of which number 

 about 10 species ar native to North America and 2 species to Pennsylvania. The members 

 of this genus are distributed widely m the northern hemisphere and extend south through 

 Central America and along the Andes mountains to Bolivia. Most of them are shrubs or small 

 trees, while a few attain a fair tree-size. 



FORM A small shrub usually from 4-10 ft. in height. Sometimes solitary, usually in clumps, 

 often forming thickets which are almost impenetrable, especially in wet locations. 



BARK Thin, smooth, fluted, astringent, at first brownish-green, later grayish-green, and 

 often covered with white blotches. 



TWIGS Rather slender, at first greenish, later greenish-brown and finally grayish-brown. 

 Often grayish-white towards end of fruiting twigs. Lenticels numerous, scattered, brownish, 

 roundish or longitudinally-elongated. Pith gieenish and irregular or triangular. 



BUDS Alternate, evidently-stalked, about J of an inch long; greenish-red, laterally com- 

 pressed, blunt-pointed, apparently covered with two valvate scales which in reality are 

 stipules. Stipular bud-scales are often whitish towards apex and usually slightly sticky. 



LEAVES Alternate, simple, obovate, blunt-pointed or rounded at apex, usually wedge- 

 shaped at base, almost regularly serrate on margin at first slightly gummy, later smooth, 

 rather thick, 2J-4J inches long; green on both surfaces, but darker on upper surface, brownish 

 pubescent below especially in the axils of the veins. Veins depressed above and ridged 

 below. 



LEAF-SCARS Alternate, raised, usually 2 or 3-ranked, somewhat triangular, containing 

 about 3 bundle-scars which are often compounded. Stipule scars narrow, triangular, brownish 

 and very close to leaf-scars. 



FLOWERS Appear in March or April before the leaves. Staminate and pistillate occur 

 separately but on same twig. Stamiuate in aments which develop partly in previous autumn 

 and remain dormant over winter. In winter they are stiff, pendant, greenish, and about 

 one inch long; in clusters of 2-5 at the end of bare stalks. Pistillate also develop in the 

 previous autumn and remain dormant over winter, are about J-5 of an inch long, usually clustered 

 in 2s or 3s and greenish to purplish in color. The first warm days of spring bring forth 

 the scarlet styles of the pistillate flowers. 



FRUIT A cone-like woody structure, about J-2 of an inch long, orbicular, persistent, 

 composed of thick and woody scales on which the little, practically wingless, round and 

 flattened nutlets are, pioduced. 



WOOD Diffuse-porous: growth rings distinct; rays variable in width. Sapwood turns 

 yellowish-brown upon exposure. 



DISTINGUISHING CHARACTERISTIC^ The Smooth Alder, also known as Black Alder, 

 can be distinguished by the woody cone-like fruit which is usually present at all seasons of 

 the year. The wet habitats which it frequents may also aid in recognizing it. In spring it is 

 one of the first of our small trees to blossom. In summer the stiff leaves with their rounded 

 apexes are also characteristic. In winter the mature fruit, developing staminate and pistillate 

 flowers, stalked buds, and triangular green pith, are distinctive. The only other Alder 

 native to Pennsylvania is the Speckled or Hoary Alder (Alnus incana (L.) Moench.) This 

 species can be distinguished from the Smooth Alder by its leaf-blades which are usually 

 glaucous or finely pubescent and rounded at the base. 



RANGE Essentially a southern species, extending from Maine to Florida and Texas and 

 westward to Minnesota. 



DISTRIBUTION IN PENNSYLVANIA Very common in the eastern and southern parts 

 of the State. Sparse and locally abundant in northern and western parts. 



HABITAT Common along streams and in swamps. Rarely ascends the hillsides. In wet 

 situations it often forms dense thickets. 



IMPORTANCE OF THE SPECIES The two species of Alder native to Pennsylvania do not 

 attain a size which would make them important commercially. They may be of value as 

 soil-binders and soil-ctnservers along the banks of streams or in very wet situations since 

 they develop large and strong roots which throw Off many suckers. 



