40 HOUGH'S AMERICAN WOODS. 



GENUS ALNUS, TOURNEFORT. 



Leaves deciduous, alternate, generally serrate, pinnately veined, furnished with 

 caducous stipules which inclose them in the bud, fall in autumn while still green 

 in color. Flowers expand in early spring with or before the leaves (or rarely in 

 autumn) in pedunculate aments, formed during the summer or autumn of the 

 previous season, from the axils of leaves or bracts and remaining naked and erect, 

 monoacious, apetalous, sessile, one to six together beneath the peltate short-stalked 

 scales of the ament. Staminate aments long, pendulous and generally in pani- 

 cles, the scales of the ament usually 2-4-flowered, the flowers subtended by 

 minute bractlets adnate to the base of the scale ; calyx usually 4-parted; 

 stamens of the same number or exceptionally half as many as the calyx-lobes 

 and opposite them, filaments erect with introrse 2-celled anthers longitudinally 

 dehiscent. Pistillate aments erect from axils below those producing the staminate 

 aments, ovoid or oblong, scales fleshy and beneath each are usually two flowers 

 subtended by minute bractlets, these aments becoming in Fruit ovoid, oblong or 

 subglobose strobiles with scales thickened at apex, woody and closely imbricated 

 over the minute brown compressed nutlet slightly or not at all winged, tipped 

 with the remnants of the style and containing a single suspended exalbuminous 

 seed. The strobiles persist for a time after liberating the seed with truncate 

 thickened scales divergent. 



Genus consists of trees and shrubs with astringent bark, watery juice and soft 

 wood very durable in water. Alnus is the ancient Latin name of the Alder. 



163. ALNUS RHOMBIFOLIA, NUTT. 

 CALIFORNIA ALDER, WHITE ALDER, MOUNTAIN ALDER. 



Ger., Californische Erie' Fr., Anue de Calif ornie; Sp., Aliso de 



California. 



SPECIFIC CHARACTERS : Leaves ovate to oval, 2 to 3 in. long, rounded or acute 

 at apex, wedge-shaped at base, serrate, generally irregularly so, and sometimes 

 doubly serrate, with spreading glandular teeth, furnished with white deciduous 

 tomentum at first but finally lustrous dark green and frequently glandular-dotted 

 above, lighter and slightly puberulous beneath, with slender yellow hairy peti- 

 oles from i to f in. long. The staminate aments which in the previous summer 

 were nearly an inch long, shining dark brown and erect, in autumn begin to 

 lengthen and by mid winter when the tree is leafless are drooping and from 4 to 6 

 in. long, in racemes with short slender stems; scales of ament orange- brown ; 

 calyx yellow, with four lobes rounded at apex and shorter than the stamens 

 which are usually two (exceptionally 1 or 3) together under each scale. Pistil- 

 late aments in short pubescent racemes do not appear until late autumn and are 

 fully developed by January; scales broad-ovate rounded at apex; styles exserted. 

 Fruit oblong strobiles to in. long, with scales thickened and lobed at apex, 

 fully grown by midsummer, but do not until the next winter open and liberate 

 their nutlets, which are broad-ovate with thin acute margins. 



(The specific name is of obscure application.) 



This Alder occasionally attains the height of 80 ft. (24 m.), with 

 straight columnar trunk 2-3 ft. (0.90 m.) in diameter, vested with a 

 thickish dark -brown bark, rough with irregular longitudinal ridges, 

 on the summits of which commonly persists the smoothish ash-gray and 

 somewhat horizontally laminated epidermis of the young bark. It 

 is particularly a conspicuous tree in winter when leafless, with its long 

 yellow catkins hanging in abundance from its slender branchlets. 



HABITAT. From the vicinity of the British boundary southward 



