238 FOREST TREES OF THE PACIFIC SLOPE. 



smooth, and slightly wrinkled by the depression of the veins on their upper sides. 

 The wide midvein is yellow. They vary in length from about 1\ to 4 inches, 

 and in width from 1 to 1J inches. The hairy seed capsules are borne in a pecu- 

 liarly dense, cylindrical cluster, from 4 to 5 inches long, while the top of the 

 capsules ends in a minutely double-forked, thread-like tip (fig. 101). 



Coast of Alaska, from Alexander Archipelago to Cape Lisbourne, and eastward to the 

 valley of the Mackenzie River and to the shores of Coronation Gulf. 



OCCURRENCE. 



Little is known of its occurrence. Bay shores in newly deposited gravel (low shrub), 

 and in gravel of older deposit (as a tree) among shrubs. Scattered, and sometimes with 

 broadleaf willow. 



Climatic Conditions. — Probably similar to those of black cottonwood. 



POPTJLUS. C0TT0NW00DS AND POPLARS. 



This large group includes the trees popularly known as aspens, poplars or 

 " popples," and cottonwoods. Several of them are very large forest trees, with 

 rough, deeply furrowed, grayish bark ("cottonwoods"), or with smooth bark, 

 little broken, and whitish or ashy (aspens). In their habits, their reproduction, 

 and, to some extent, their foliage, they are closely related to the willows, with 

 which they are most often associated. The leaves grow singly at alternate 

 points on the branches, as in the willows. In outline, many of them are remotely 

 triangular or egg-shaped, sometimes lance-shaped — very closely resembling the 

 pointed-leafed willows ; the borders of the leaves either have small, hooked, 

 blunt teeth or are entire (uncut). When mature, they are most often smooth 

 on both surfaces, but occasional species have hairy or woolly leaves. The leaf 

 stems of many species are flattened at right angles to the leaf blade, and this 

 causes the leaves to tremble in the slighest breeze. The leaves, after turning 

 yellow, fall from the trees in autumn, leaving prominent leaf scars which give 

 the twigs a knotty appearance. The scaly buds of many species are character- 

 ized by a covering of pungent, sticky resin. & which appears to have a protective 

 use. Male and female flowers are each borne on separate c trees ; only the female 

 trees produce seed. Trees of the two sexes are unevenly distributed — fre- 

 quently only one seed tree to many male or sterile trees ; sometimes they are 

 very widely separated. The flowers are fertilized by insects. With one or two 

 exceptions (in female flowers), the flowers of each kind appear in long cylin- 

 drical clusters, which hang down conspicuously from the bases of buds on twigs 

 of the previous year's growth. The seed-bearing flowers develop bud-like cap- 

 sules (arranged on a pendent, thread-like stem) which are usually mature in 

 early spring, before or by the time the leaves are full grown. Soon afterwards 

 the capsules split open by from 2 to 4 divisions and liberate their minute, cot- 

 tony seeds. These are provided with exceedingly fine, silky, white hairs, which 

 render them very buoyant, so that the wind may bear them many miles from the 

 parent trees. Of all trees, this group, together with the willows, is best 



" IAriodendron tulipifera L., native of the East, more properly called tulip-tree, is often 

 known as " poplar " or " yellow poplar." It is a member of the magnolia family and in 

 no way related to the true poplars. 



b The so-called " bee glue," with which honey bees fasten their honey combs in hives 

 or in the hollows of trees, is gathered by bees from the buds of the cottonwoods. When 

 hard, it is very strong. 



c Sometimes one tree may produce clusters of male and of female flowers, or even. 

 clusters combining both male and female flowers, but this is exceptional. 



