GENUS 5. 



BIRCH FAMILY. 



613 



2. Alnus incana (L.) Willd. Spreckled or 

 Hoary Alder. Fig. 1507. 



Betnla Alnus var. incana L. Sp. PI. Ed. 2, 1394. 1763. 

 Alnus incana Willd. Sp. PI. 4: 335. 1805. 



A shrub, or rarely a small tree, 8-4O high, the 

 twigs glabrous, the young shoots pubescent. Leaves 

 oval or ovate, acute or sometimes obtuse at the apex, 

 finely serrulate or dentate, with the teeth serrulate, 

 obtuse or some of them acute at the base, dark green 

 above, pale or glaucous and pubescent, at least on 

 the veins beneath, 2'-$' long, 1^-4' wide, the veins 

 prominent on the lower surface; stipules oblong- 

 lanceolate, deciduous; petioles 4" -12" long; aments 

 unfolding much before the leaves, the staminate i- 

 3' long, the pistillate ovoid, about long and 3"~5" 

 in diameter in fruit, their bracts 5-toothed; nut or- 

 bicular, coriaceous-margined. 



In wet soil, Newfoundland to Saskatchewan, New 

 York, Pennsylvania and Nebraska. Also in Europe and 

 Asia. Wood soft, light brown ; weight per cubic foot 28 

 Ibs. Black or tag-alder. April-May. 



3. Alnus rugosa (DuRoi) Spreng. Smooth 

 or Hazel Alder. Fig. 1508. 



Bcinla Alnus rugosa DuRoi, Harbk. I: 112. 1771. 

 Alnus serrulata Willd. Sp. PI. 4: 336. 1805. 

 Alnus rugosa Spreng. Syst. 3: 848. 1826. 



A shrub S-2O tall, or sometimes a small tree, 

 attaining a maximum height of 40 and a trunk 

 diameter of 6', the bark smooth, the younger shoots 

 somewhat pubescent. Leaves green on both sides, 

 obovate or oval, mostly obtuse and rounded at the 

 apex, narrowed or rounded at the base, sharply and 

 minutely serrulate, when mature glabrous above, 

 usually pubescent beneath, at least on the veins, 3'~5' 

 long, stipules oval, deciduous; petioles 4"- 12" long; 

 aments unfolding much before the leaves (or in the 

 South after the leaves), the staminate 2' -4' long, the 

 pistillate ovoid, 6"-9" long in fruit; nut ovate, nar- 

 rowly coriaceous-margined. 



In wet soil, or on hillsides, Maine to Ohio and Minne- 

 sota, Florida and Texas. Wood soft, light brown; 

 weight per cubic foot 29 Ibs. Common, tag, american 

 or green alder. March-April. 

 Alnus noveboracensis Britton, has leaves acute at both ends and densely pubescent on the 

 veins beneath. It may be a race of this species. It is known certainly only from a Staten Island 

 tree, now destroyed. 

 f 



4. Alnus Alnus (L. ) Britton. European 

 Alder. Eller. Fig. 1509. 



Betula Alnus and var. gluthwsa L. Sp. PI. 983. 1753. 

 Alnus vitlgaris Hill, Brit. Herb. 510. 1756. 

 Alnus giutinosa Gaertn. Fr. & Sem. 2: 54. 1791. 



A tree, reaching a maximum height of about 

 75 and a trunk diameter of 2.\ , the bark smooth, 

 the branches nearly horizontal, the foliage gluti- 

 nous. Leaves broadly oval, orbicular or obovate, 

 thick, dark green, dull, often obtuse at both ends, 

 coarsely dentate and the teeth denticulate, gla- 

 brous above, pubescent on the veins beneath, 2'-$' 

 long; petioles A'-i' long; aments appearing from 

 naked buds, expanding much before the leaves, 

 the staminate 3 '-4' long, the pistillate ovoid- 

 oblong, 6"-g" long in fruit ; nut wingless, coria- 

 ceous-margined. 



In wet places, Newfoundland to New Jersey and 

 Illinois, escaped from cultivation. Native of Europe. 

 Wood soft, brown ; weight per cubic foot 35 Ibs. 

 Irish mahogany. Hollard. Ooler. Black alder. 

 April. 



