FOREST TREES OF THE PACIFIC SLOPE. 99 



Best stands on flats, gentle slopes, heads of moist valleys, or in sheltered ravines 

 (below Crater Lake in Cascades of southern" Oregon). Decidedly prefers north exposures, 

 doubtless on account of less heat and greater soil moisture there Exposed high slopes 

 least favorable to best growth; although often abundant there, it is usually stunted.- 

 Commonly in limited pure stands and in mixture. At north, with Sitka spruce, western 

 hemlock, and alpine fir. Southward, at high altitudes, with white-bark pine, alpine fir, 

 Lyall larch. L'ngelmann spruce, while grand fir, lodgepole and western white pines are 

 also occasional associates at lower elevations. Large pure stands are uncommon, but 

 rather extensive forests with 85 per cent of hemlock are occasional. Lure patches are 

 frequent on north slopes. In southern Alaska and British Columbia, with spruce, firs, 

 poplars, and birches. At high altitudes in California, often in groups with patches 

 of white-hark pine; lower, commonly with California red fir and lodgepole and western 

 white pines. 



Climatic Conditions. — Endures severe alpine climate. Daily and seasonal ranges 

 of temperature great, owing to intense sunlight and rapid radiation of heat at night. 

 Rarity of air, together with frequent high winds, cause rapid transpiration, which is 

 modiued somewhat by increased humidity due to low air temperature. Precipitation, 

 large; chiefly snow, which often buries trees. Snow comes early and stays late; melting 

 slowly, it supplies moisture throughout the short growing season. Rains are rather fre- 

 quent in spring and fall, hut summers are usually hot and dry, especially on south 

 exposures. 



Tolerance. — Very tolerant ; excepting western hemlock, surpassing all associates in 

 shade endurance. Its dense shade, almost excluding light from ground, usually prevents 

 growth of seedlings, even its own. which appear to require more light than the heavy 

 shade of mother trees affords, but which thrive under lodgepole pine, fir, etc. • Seedlings 

 and saplings hear long suppression, and rarely die under it. Trunks are not cleared 

 readily, even in dense stands; dead branches usually persist or leave short stubs which 

 form loose knots in timber. 



Reproduction. — Prolific seeder, producing cones when about 20 years old; seed is 

 borne annually, but not every year is a good seed year. Seed has only moderate rate of 

 germination, and its vitality is rather transient. With sufficient moisture, seed ger- 

 minates on both humus and mineral soils, but apparently better on latter. Seedlings 

 grow better In moderate shade and moist humous soil than in full light. 



PSEUDOTSUGA. FALSE HEMLOCKS. 



The generic name of the false hemlocks indicates a relationship to the hem- 

 locks, which they resemhle in the distinctly formed leaf "stems and in the habit 

 and character of their cones. The rosin vesicles of hemlock seeds tire, how- 

 ever, absent from the seeds of Pseudotsugas. The latter have small resin- 

 pockets, or "blisters," in the bark of young trunks and branches, in this respeel 

 being similar to the firs. Woodsmen and lumbermen know them as " varieties" 

 of " fir " or " spruce," and even as " pines." Properly they should not be called 

 lirs. from which they differ greatly in the character of their wood, foliage, and 

 cones. The superficial resemblance of the wood of these trees to pine is a 

 popular reason for calling them pines, but it is a perversion of the name, for in 

 all respects the pines are totally different trees. 



False hemlocks are evergreen trees with dense, soft, flat leaves. Their 

 branches, growing in irregular circles, form with their many side-branches wide, 

 fan-like, densely foliaged sprays. The rough, very thick-barked trunks are tall 

 and massive, and taper slowly. They have broadly pyramidal crowns, which in 

 young trees extend to the ground. The Hat. bluntish leaves, attached by dis- 

 tinct steins, arc spirally and singly arranged on the branches. They appear often 

 to grow mainly from two opposite sides and from the top of the branch; but 

 lower leaves bend upward toward each side of the branch by a twist in their 

 steins. Leaves of a season's growth remain on the tree about live or eight 

 years. In cross-section the leaves of our species show two resin-ducts on the 

 under margin near the edges of the leaves. Flowers of two sexes are borne 

 Singly on branchlefs, formed the previous year, on different parts of the same 

 tree. The female flowers are bristly, scaly bodies, developing into cones with 



