938 The Trees of Great Britain and Ireland 



nerves, with conspicuous tufts of rusty-brown hairs in the axils ; petioles, glabrous 

 or pubescent, 4 to i inch long; stipules conspicuous, deciduous, ovate to lanceolate, 

 obtuse, fringed with glandular hairs. The leaves turn blackish in autumn. 



Flowers appearing very early, before the leaves, in February or March. 

 Catkins, three to six in a raceme, at the tip of a branchlet. Staminate catkins, 2 to 4 

 inches long, at first erect and rigid, afterwards lax and pendent ; stamens,' four, 

 yellow, opposite the segments of the four-lobed calyx. Pistillate catkins, always 

 erect, at first about i inch long, smooth, with reddish-brown stigmas ; afterwards 

 1 inch long, ovoid, cone-like, the scales ending in purple shield-like expansions, each 

 with a central brown point. Cones at first green, ultimately black, persistent on the 

 tree after the escape of the nutlets. Nutlets obovate, blunt-angled, wingless or 

 with a very narrow coriaceous wing. 



The nuriets ^ are gradually shaken out of the cones by the wind during autumn 

 and winter. Their walls are provided with small air-tight cavities, which enable them 

 to float in water, and secrete an oil, which protects them from being wetted. 

 Usually falling into streams and ditches, they float undamaged and unchanged during 

 winter, and germinate in the water in early spring. The young seedlings, drifting to 

 the bank, establish themselves where they happen to be stranded in a suitable 

 place. 



In winter, the twigs are glabrous and usually covered with a thin waxy secretion. 

 Leaf-scars pentagonal or rhomboid, parallel to the twig on a projecting cushion, five- 

 dotted, the lowermost three dots coalesced together. Stipule-scars linear, one on 

 each side of a leaf-scar. Terminal bud present, similar to the lateral buds ; all 

 conspicuously stalked, ovoid, obtuse, with two external scales, viscid-glandular, and 

 often covered with a purplish bloom. Pith triangular in section. 



The common alder coppices freely from the stool ; but rarely if ever produces 

 root-suckers. 



Varieties 



The common alder, distributed over a wide area, shows considerable variation 

 in the wild state, and several varieties have been described. 



I. Var. Sardaia, Ledebour, F/. Rossica, iii. 657 (1851); Wxv^&r, BetulacecB, 118 

 (1904). Alnus barbata, C. A. Meyer, Vers. Pfl. Kauk. 43 (183 1). 



This variety is remarkably distinct in the foliage, but has the flowers and fruit 

 of typical A. glutinosa. Young branchlets pubescent. Leaves, about 3 inches long 

 and 2 inches wide, rounded at the base, rounded or occasionally acute at the apex, 

 margin with serrate lobules, ciliate ; nerves eight or nine pairs, running parallel and 

 curved to the margin ; upper surface dark green, shining, minutely pubescent ; lower 

 surface pubescent, the pubescence densest along the midrib and nerves ; petiole | 

 mch, pubescent. Buds pubescent. 



nolliltfnT"'i°.TK ^"'" ^'''"*'' ^'^- ''^°'- "• PP- "9. 133, 135, gives an elaborate account of the way in which 

 poUmation ^effected by the wind, and of the devices for the protection of the pollen in rainy weather. 

 Lf. Miall s account of the fruit of the alder in Round The Year, p. 279. 



