254 FOREST TREES OF THE PACIFIC SLOPE. 



BETULTJS. BIRCHES. 



Without exception, the tree and shrubs of this group are called birches. 

 In most of the species the bark of young trees is smooth and often sep- 

 arable into paper-like sheets of a chalky-white, yellow, orange-brown, red- 

 brown, or copper color; one or two species, however, have gray-brown bark, 

 not separable into layers. Old trees have furrowed, scaly bark. The. fine, 

 dense structure of the hard wood and its comparatively indistinct annual 

 layers are also characteristic, while most birches have beautiful, reddish- 

 brown heartwood, which is commercially of great value. The very fine, 

 round twigs are conspicuously marked by long-persistent, light-colored spots. 

 Year-old twigs produce, the succeeding year, two leaves from the side buds, 

 while from the end bud a new shoot grows with only one leaf at a point. 

 Young twigs and the inner bark of several birches have a fragrant, winter- 

 green taste when bruised or chewed (they are not poisonous). The cylindrical 

 male flower clusters, partly matured the previous summer and so remaining until 

 early spring, one or several together, are long, tassel-like bodies hanging do\Vn 

 from the ends of the twigs, back of which the very much smaller, cylindrical, 

 quite or nearly erect female flowers proceed from the short, 2-leafed, thorn-like 

 side twigs. Flowers appear before or with the growing leaves ; female clusters 

 develop into cylindrical or elongated cones, under the scales of which are borne 

 very minute, brownish seeds with two gauze-like wings. The cones mature and 

 fall to pieces in late spring or early summer, leaving on the twig a central 

 thread-like stem, to which the scales were attached. Sown thus early, the 

 seeds germinate at once in moist, shady places, and the seedlings mature suffi- 

 ciently that season to pass the winter safely. It is best, if possible, to sow birch 

 seed soon after it is gathered, since by storing it until the following spring 

 much of its germinating power may be lost. 



Few of the Pacific birches are of importance for their wood, because within 

 the region most of them are too small or infrequent to form stands sufficient 

 to supply commercial or domestic uses. When they occur with a few other small 

 trees, they are useful as a protective cover on canyon streams, but otherwise they 

 are unimportant for the forester. Eastern and northern representatives of the 

 group are much more important forest and timber trees. 



The birches from which our species descended existed in early geologic times. 

 Remains of them are found in the Cretaceous rocks of the Dakota formation 

 and in the more recent Tertiary formations. In Tertiary times they inhabited 

 the north central and northwest coast region of this continent. Many species, 

 now extinct, also existed in Europe during the Eocene and Miocene periods. 



Nine tree birches grow in the United States and adjacent Canadian ter- 

 ritory, of which four inhabit the Pacific region. 



Western Birch. 

 Bet ula occidentalis Hooker. 



DISTINGUISHING CHARACTERISTICS. 



Very much confusion has existed regarding the identity of the true Betula 

 occidentalis, which, so far as now known, occurs only in northwestern Wash- 

 ington and adjacent territory in British Columbia. To Prof. C. S. Sargent 



° The last bud on a season's twig is not strictly a terminal bud, such as is produced by 

 oaks, pines, etc., but a side or lateral bud, which appears terminal because the immature 

 terminal part of the shoot dies and. falls late in autumn or in winter. This is true of 

 all birches. 



