512 



BETULACEAE. 



(Fig. 1 22 1.) 



i. Alnus Alnobetula (Ehrh.) K.Koch. Green or Mountain Alder. (Fig.i22o.) 



Betula Alnobetula Ehrh. Beitr. 2: 72. 1788. 



Betula viridis Chaix; Vill. Hist. PI. Dauph. 3: 789. 1789. 



Alnus viridis DC. Fl. Fr. 3: 304. 1805. 



Alnus Alnobetula K. Koch, Dendr. 2: Part i, 625. 1872. 



A shrub, 2-io high, the young foliage glutinous 

 and more or less pubescent. Leaves oval or ovate, 

 obtuse or acute, sharply and more or less irregularly 

 serrulate or incised-serrulate, when mature dark 

 green and glabrous above, light-green and usually 

 pubescent on the veins beneath, 2'-$' long, ij4'-3 r 

 wide; petioles 4 // -i2 // long; aments expanding with 

 the leaves, the staminate slender, naked, i^ / -2^ / 

 long, the pistillate from scaly buds, oblong or ovoid- 

 oblong,slender-peduncled,becoming 6 // -8 // long and 

 4 // -5 // in diameter in fruit, their bracts irregularly 5- 

 toothed; nut oblong, the thin wings about as broad 

 as the body. 



Newfoundland to Alaska, Massachusetts, New York, 

 Michigan and British Columbia, and in the higher Alle- 

 ghanies of Virginia and North Carolina. Also in Europe 

 and Asia. June. 



2. Alnus incana (L.) Willd. Speckled or Hoary Alder. 



Betula 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, 8-25 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 1 east on 

 the veins beneath, 2 / -5 / long, i %'-$.' wide, the veins 

 prominent on the lower surface; stipules oblong- 

 lanceolate, deciduous; petioles 4 // -i2 // long; aments 

 appearing from naked buds, unfolding much before 

 the leaves, the staminate iK / ~3 / l n g> the pistillate 

 ovoid, about y 2 r long and 3 // -5 // in diameter in fruit, 

 their bracts 5-toothed; nut orbicular, coriaceous- 

 margined. 



In wet soil, Newfoundland to the Northwest Terri- 

 tory, south to southern New York, Pennsylvania and 

 Nebraska. Also in Europe and Asia. Wood soft, light 

 brown; weight per cubic foot 28 Ibs. April-May. 



3. Alnus rugosa (DuRoi) K. Koch. Smooth Alder. (Fig. 1222.) 



Betula Alnus rugosa DuRoi, Harbk. i: 112. 1771. 

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

 Alnus rugosa K. Koch, Dendr. 2: Part i, 635. 



A shrub 5-2o 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 on the veins be- 

 neath, 3 '-5' long, stipules oval, deciduous; petioles 

 4 // -l2 // long; aments appearing from naked buds, 

 unfolding much before the leaves (or in the South 

 after the leaves), the staminate 2'-$' long, the pis- 

 tillate ovoid, 6 // -9 // long in fruit; nut ovate, nar- 

 rowly coriaceous-margined. 



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

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

 weight per cubic foot 29 Ibs. March-April. 





