CONIFEES OF THE ROCKY MOUNTAIN REGION. 7 



single fibrovascular bundle in the center and no resin ducts. The 

 number of leaves in a cluster (PL II), which can not be depended upon 

 as a distinctive characteristic, ranges from 14 to about 30. 



The cones (PI. II) mature in one season, being ripe during the latter 

 part of August and early in September. They open soon afterwards 

 and shed their hght chestnut-brown seeds (PI. II, a). By the end of 

 October or November aU of the cones have fallen from the trees. 

 The cones are borne on very short footstalks and vary in length from 

 about 1 inch to 1^ inches. The cone scales are usually densely coated 

 on the outside below the center with dehcate, whitish, woolly hairs. 

 The seed-leaves of western larch are, as a rule, 6 in number (PI. II, 6, c) . 



The commercially valuable wood is of a clear reddish brown color, 

 and usually narrow-ringed, with a comparatively thin layer of 

 whitish sapwood. It is strong, and very durable in an unprotected 

 state, differing greatly in the latter respect from wood of the eastern 

 larch (Larix laricina). Western larch wood is much used locally 

 for lumber and for rails and shakes. The largest general use, however, 

 is for telegraph and telephone poles, railway ties, and posts. It is the 

 heaviest of our larch woods, a cubic foot of the dry wood weighing 

 a little over 46 pounds. 



OCCURRENCE AND HABITS. 



Larix occidentalis grows on mountain slopes, preferring north and 

 west exposure, stream bottoms, valleys, and flats at elevations 

 between about 2,000 and 7,000 feet. It is rare in the bottoms of 

 canyons and on the summits of mountains (Map No. 2)}^ As the 

 tree is very exacting in its requirements of soil moisture, the best 

 growth occurs in deep, fresh, porous soils; it will, however, maintain 

 itself in low, moist places and in dry, gravelly soils. 



Western larch sometimes forms pure stands, but it usually occurs 

 mixed with other trees. Its best growth is in northeastern Washing- 

 ton, northern Idaho, and northwestern Montana, where it often 

 occurs in pure open forests in valleys and on slopes. Trees of largest 

 size are found at lower elevations along Priest River (Idaho) in 

 mixture with western white pine, western red cedar, Douglas fir, 

 western hemlock, Engelmann spruce, and lowland white fir. Some- 

 what higher up it becomes an important part of Douglas fir forests, 

 here being associated with lodgepole pine, western white pine, 

 lowland white fir, alpine fir, and Engelmann spruce. In the Bitter- 

 root Mountains (northern Idaho), it grows in pure stands or is mingled 

 with small numbers of Douglas fir and western yellow pine. 



Western larch is very intolerant of shade throughout Hfe, probably 

 demanding even more light than western yellow pine. The dis- 



16 The author's cordial thanks are due to Dr. H. N. Whitford for valuable notes extending the range of 

 Larix occidentalis in British Columbia. 



