CHAP. CIV. BETULA'CEJE. yf'LNUS. 1677 



CHAP. CIV. 



OF THE HARDY LIGNEOUS PLANTS OF THE ORDER BETULA^CEJE. 



These are included in two genera, the characters of which are thus given 

 by Smith : — 



-4'lnus Tourn. Barren flowers numerous, aggregate, in a loose cylin- 

 drical catkin, imbricated every way. Calyx a permanent wedge-shaped 

 scale, 3-flowered, with 2 very minute lateral scales. Corolla composed of 

 3 equal florets, attached to the inner side of every scale, each of one petal, 

 in 4 deep, equal, ovate, obtuse segments. Filaments 4, from the tube of 

 the corolla, shorter than its segments, and opposite to them. Anthers of 

 2 round lobes. — Fertile flowers fewer, aggregate, in an oval firm catkin, 

 imbricated every way. Calyx a permanent, wedge-shaped scale, 2-flowered. 

 Corolla none. Germen compressed, of 2 cells. Styles 2, parallel, taper- 

 ing, a little prominent, deciduous. Stigma simple. Nut ovate, bony, 

 compressed, angular, without wings, of 2 cells. Kernels solitary, ovate, 

 acute. — Trees, with leaves alternate, stalked, simple, wavy or cut, decidu- 

 ous, with twin deciduous stipules. Catkins terminal, panicled, pendulous, 

 earlier than the foliage. (Eng. Fl. y iv. p. 134.) Natives of Europe and 

 North America. 

 j5e"tula Tourn. Barren flowers. Catkin cylindrical, lax, imbricated all 

 round with ternate concave scales; the middle one largest, ovate. Co- 

 rolla none. Filaments 10 — 12, shorter than the middle scale, to which 

 they are attached. Anthers roundish, 2-lobed. — Fertile flowers. Catkin 

 similar, but more dense; scales horizontal, peltate, dilated outwards, 3- 

 lobed, 3-flowered. Corolla none. Germen compressed, bordered, of 2 

 cells. Styles 2, awl-shaped, downy. Stigma simple. Nut oblong, decidu- 

 ous, winged at each side, of one cell, with a solitary kernel. — Trees or 

 shrubs, very hardy, with round slender branches ; scattered, stalked, simple, 

 serrated, deciduous leaves; and a hard, often veiny, wood. Bark, in 

 several species, of many fine, soft, membranous layers. {Eng. Fl. t iv. 

 p. 153.) Natives of Europe, North America, and Asia. 

 The alder and the birch were made separate genera by Tournefort, and by 

 Linnaeus also, in his earlier works; but he afterwards united both genera 

 into one, under the name of 2?etulus. Modern botanists, for the most 

 part, follow Tournefort; and the following are the distinctive character- 

 istics of his two genera: — In Z?etula, the female catkins are cylindrical, 

 solitary, on simple peduncles, and bear their seeds furnished with a mem- 

 brane on each side. In zTlnus, the female catkins are oval ; and they are 

 borne on a branchy peduncle, containing seeds which are not bordered 

 with membranes. As secondary characteristics, the birches prefer dry 

 places, and the alders moist situations. All the known species of alder 

 may be reduced to three or four; and all the species of birch which are 

 hardy in England to four or five. Most of the species of both genera 

 flower and fruit freely in the climate of London. 



Genus I. 



il±j 



^4'LNUS Tourn. The Alder. Lin. Syst. Monce'cia Tetrandria. 



Identification. Tourn., t. 359.; Willd. Sp. PI., 4. p. 334. : Hall. Hist, 2. p. 300.: Comp., ed. 4., 



p. 176. ; Gaertn., t. 90. 

 Synonymes. jSetulae species Lin. ; Aune, Fr. ; Erie, Ger. ; Ontano, Ital. ; Aliso, Span. 

 Derivation. From at, near, and tan, the edge of a river, Celtic ; in reference to its habitat : 



from the Hebrew, alon, an oak : or, according to others, from aliiur a?nne, it thrives by the 



river. 



