68 SILVA OF NORTH AMERICA. BETULACEZ. 
furnished with a narrow wing-like membranaceous border; pericarp of two coats, the outer thin and 
Seed solitary by abortion, filling the cavity of the 
nut, suspended, exalbuminous ; testa membranaceous, light brown; cotyledons fleshy, flat, much longer 
membranaceous, the inner thicker and crustaceous. 
than the short superior radicle turned toward the minute apical hilum.’ 
An inhabitant of swamps and river-bottoms and high mountain slopes, and often, especially in 
northern Europe and Asia, a conspicuous feature of vegetation, Alnus is widely and generally distributed 
through the boreal and temperate regions of the northern hemisphere, ranging at high elevations 
southward in the New World through Central America to Colombia, Peru, and Bolivia,? and to upper 
Assam in the Old World.’ Fifteen species and many varieties are now distinguished.* 
Of the North 
American species five attain the size and habit of trees, and three, Alnus Alnobetula,’ Alnus incana,® 
1 The species of Alnus may be grouped in the following sections : 
ALNASTER (Endlicher, Gen. Suppl. iv. pt. ii. 20. — Prantl, Engler 
& Prantl Pflanzenfam. iii. pt. i. 45 [subgen. Alnobetula, K. Koch, 
Dendr. ii. pt. i. 625]). Flowers in three-flowered clusters appear- 
ing in spring with the leaves. Staminate aments solitary or in 
pairs, naked during the winter ; pistillate aments pedunculate, in 
terminal panicles on short two or three-leaved branchlets, covered 
during the winter ; calyx of the staminate flower regularly four- 
lobed. Nut surrounded by a broad thin wing. Inhabitants of 
eastern North America, Europe, northern Asia, and Japan. 
CLerHROpSIS (Endlicher, J. c. — Prantl, J. c.). Flowers appear- 
Stam- 
inate aments elongated, pedunculate, the pistillate racemose or soli- 
ing in spring with the unfolding of the leaves, or in autumn. 
tary ; calyx of the staminate flower from ten to twelve-parted, 
the divisions scale-like, unequal. Nut surrounded by a narrow 
wing. Inhabitants of the temperate Himalayas. 
Aunus (Endlicher, J. c. [secs. Phyllothyrsus and Gymnothyr- 
sus].— Spach, Ann. Sci. Nat. sér. 2, xv. 204 [Revisio Betulacea- 
rum]. — Regel, De Candolle Prodr. xvi. pt. ii. 183, 184 [sec. 
Gymnothyrsus.]— Prantl, 1. c. 46). 
spring before the unfolding of the leaves from paniculate or race- 
Flowers appearing in the 
mose aments formed during the summer, and naked, or the pistil- 
late rarely covered during the winter, or (Alnus maritima) appear- 
ing in autumn in aments of the season, the pistillate usually 
solitary ; calyx of the staminate flower regularly four - parted ; 
stamens four or rarely two or three. Nut wingless or surrounded 
Inhabitants of North and South 
America, Europe, northern Africa, western and northern Asia. 
2 Humboldt, Bonpland & Kunth, Nov. Gen. et Spec. ii. 20.— 
Kunth, Syn. Pl. Zquin. i. 363. — Mirbel, Mém. Mus. xiv. 463. — 
Hemsley, Bot. Biol. Am. Cent. iii. 165. 
8 Hooker f. Fl. Brit. Ind. v. 600. 
* Spach, J. c. 200. — Endlicher, 7. c. 20.— Regel, Nouv. Mém. 
Soc. Nat. Mose. xiii. 131 (Monographia Betulacearum) ; Bull. Soc. 
Nat. Mose. xxxviii. pt. ii. 419 (Gattungen Betula und Alnus) ; De 
Candolle Prodr. l. c. 180. 
Several plants thought to be intermediate in character between 
by a narrow coriaceous border. 
species of Alnus have been noticed ; they are believed by some 
European botanists to be natural hybrids, while others consider 
them varieties. The best known of these plants is Alnus pubescens 
(Tausch, Flora, xvii. pt. ii. 520 [1834]. — Regel, De Candolle 
Prodr. 1. c. 187), a supposed hybrid between Alnus glutinosa and 
Alnus incana, known in several localities from Lapland to the 
Caucasus. (See, also, for hybrids of Alnus, K. Koch, J. c. 637. — 
Dippel, Handb. Laubholzk. ii. 162. — Koehne, Deutsche Dendr. 
114, 115.) 
5 K. Koch, 2. c. 625 (1872). — Otto Kuntze, Rev. Gen. Pl. ii. 
639. 
Betula Alnobetula, Ehrhart, Beitr. 11. 72 (1788). 
Betula viridis, Villars, Hist. Pl. Dauph. iu. pt. ii. 789 (1789). 
Betula ovata, Schrank, Baier. Fl. i. 419 (1789). 
Betula crispa, Aiton, Hort. Kew. iii. 339 (1789). — Michaux, 
Fl. Bor.-Am. ii. 181. 
Alnus alpina, Borkhausen, Handb. Forstbot. i. 477 (1800). 
Alnus viridis, De Candolle, Lamarck Fl. Frang. ed. 3, iii. 304 
(1805). — Chamisso, Linnea, vi. 538. — Hooker, Fl. Bor.-Am. 
ii. 157. — Torrey, Fl. N. Y. ii. 203, t. 116. — Reichenbach, Icon. 
Fl. German, xii. 3, t. 628. — Regel, De Candolle Prodr. I. c. 181. — 
Parlatore, Fl. Ital. iv. 130. — Franchet, Nouv. Arch. Mus. v. 281 
(Pl. David. i.). — Macoun, Cat. Can. Pl. 438. — Watson & Coul- 
ter, Gray’s Man. ed. 6, 473.— Hempel & Wilhelm, Baume und 
Strducher, ii. 17, f. 126, t. 14. 
Alnus undulata, Willdenow, Spec. iv. pt. i. 336 (1805). 
Alnus crispa, Pursh, Fl. Am. Sept. ii. 623 (1814). — Gray, Am. 
Jour. Sci. xlii. 42. — Tuckerman, Am. Jour. Sci. xlv. 33. 
Alnus ovata, Guimpel, Willdenow & Hayne, Abbild. Holz. ii. 
199, t. 147 (1820).— Watson, Dendr. Brit. ii. 96, t. 96 ; Lod- 
diges Bot. Cab. xii. t. 141.— Hartig, Forst. Culturpfl. Deutschl. 
372, t. 26. 
Alnaster viridis, Spach, J. v. 201 (1841). 
Alnus incana, Hooker & Arnott, Bot. Voy. Beechey, 117, 129 
(not Willdenow) (1832). 
Alnus fruticosa, Ruprecht, Fl. Samoj. Cisur. 53 (1845). 
Alnaster fruticosus, Ledebour, Fl. Ross. iii. 655 (1849). 
Alnus Brembana, Rota, Prosp. Prov. Bergamasco, 79 (1855). 
Alnus glutinosa, y Sibirica, Miquel, Ann. Mus. Lugd. Bat. iii. 
194 (Prol. Fl. Jap.) (1867). 
Alnus Alnobetula, which is a shrub two or three feet high, or 
sometimes on the mountains of northern Japan attains the height 
of fifteen or twenty feet and assumes the habit of a tree (Alnus 
viridis, B Sibirica, Regel, Nouv. Mém. Soc. Nat. Mosc. l. c. 137. — 
Sargent, Forest Fl. Japan, 63), inhabits the Arctic Circle and high 
mountain slopes in the northern hemisphere. In America it is a 
common plant in all the north from Newfoundland and Labrador 
to Alaska, and in the United States grows on the mountains of 
New England and New York, along the coast of Maine, in north- 
ern Minnesota, and on the high peaks of the southern Alleghany 
Mountains in Carolina and Tennessee. 
§ Willdenow, Spec. 1. c. 335 (1805) ; Enum. 965; Berl. Baumz. 
ed. 2,20. — De Candolle, /. c. — Hornemann, Fl. Dan. xiii. t. 2301. — 
Emerson, Trees Mass. 220; ed. 2, i. 251, t. — Hooker f. 1. c. 
157. — Spach, l. c. 206. — Nuttall, Sylva, i. 30. — Tuckerman, 1. c. 
32. — Torrey, J. c. 202. — Ledebour, /. c. 656. — Reichenbach, l. c. 
4, t. 629, 630. — Hartig, 1. c. 368, t. 24. — Maximowiez, Mém. 
Sav. Etr. Acad. Sci. St. Pétersbourg, ix. 258 (Prim. Fl. Amur.).— 
Parlatore, Fl. Ital. iv. 128. — K. Koch, 1. c. 636. — Franchet & Sava- 
