14 BULLETIN 285, U. S. DEPARTMENT OF AGRICULTURE. 



an efficient helicopter, which, in a light breeze, may bear its load of 

 seed a hundred yards or more. The seedlings of basswood and elm 

 are able to endure moderate shade for 5 or 6 years, but seedlings of 

 greater age are rare in the virgin forest except where the crown 

 cover is broken. 



Forest-grown beech, birch, and maple seedlings which receive but 

 little light develop into extremely slender, whip-like saplings, able 

 to stand erect only through the protection of surrounding trees. If 

 very gradually exposed by frequent, light thinnings these may 

 eventually reach dominant positions; but in silviculture it is prob- 

 ably best in most cases to sacrifice these and secure fresh reproduc- 

 tion under greater light. (PI. VII, fig. 1, and PL XIV, fig. 1.) 



Within the ranges of red spruce, fir, and hemlock, the culling of 

 these species from the mixed hardwood and softwood stand reduces 

 the seed supply and thereby the proportion of softwoods in the 

 young growth. Although extremely tolerant, hemlock and spruce 

 seedlings are dwarfed, if not killed, by the heavy shade from an 

 unbroken cover of maple and beech crowns, and can succeed only 

 where the shade is lighter, as may be the case under yellow birch 

 crowns. (PL VIII.) This is also true of more or less clear cuttings in 

 these woods, for the softwood seedlings are handicapped by their very 

 slow growth in competition with hardwood sprouts and seedlings 

 and with shade-producing underbrush. In spite of this, the soft- 

 wood reproduction will usually find enough light here and there to 

 persist and in the course of time reappear in the crown cover. In 

 the mountains, the hardwoods and hemlocks are favored by the 

 relatively warm climate and deep, fertile soils of moderate altitude; 

 at higher altitudes the stands are less dense and reproduction less 

 aggressive, so that spruce and fir assume predominance without 

 much difficulty. 



Size j rate of growth, and longevity. — The "intensive reproducers" 

 are, as a rule, larger and longer-lived than the "extensive," and 

 the less tolerant of them owe their presence among shade enduring 

 species in virgin stands largely to these two attributes. They must 

 have started before or at the same time as their tolerant neighbors, 

 and kept a dominant position by faster growth and larger size; or 

 have taken advantage of accidents to trees in the stand and sprung 

 up under the increased fight thus admitted. Long-lived trees 

 naturally have more chances to establish reproduction under such 

 conditions than short-lived. White pine, white elm, white ash, and 

 basswood owe their presence among heavy-foliaged species largely 

 to these qualities. In the virgin forest they are almost always taller 

 than the surrounding hardwoods, and this affords them plenty of 

 light for seed bearing. The elm is especially favored by its wide- 

 spreading crown. (PL III, fig. 2.) Yellow birch, though of less 



