THE WESTERN VALLEYS 121 



sometimes find two stories, the upper consisting* of the crowns 

 of the vigorous larch, the lower a uniform stand of spruce. If 

 it were not for the relative growth in height of the two species 

 such a mixed stand would be impossible. 



The larch is severely subject to the attacks of Tramctes pini, 

 but even so may continue to live for years with ever diminishing 

 increment of growth, before the stem finally gives way. Other 

 fungi are likewise parasitic on the larch but they apparently are 

 less serious in their effects, and the mistletoe, Razoumofskya 

 laricis, is in some localities very troublesome. 



One of the most significant of the forest societies of 

 western Montana is that furnished by the white pine (Pinus mon- 

 ticola) and its associates. Some of the species often associated 

 are Abies grandix, Tsuga lieterophylla, Thuja plicata, Taxus 

 brevifolia, Betula papi/rifera, Populus trichocarpa, Lonicera in- 

 volucrata, Lonic< ru dlona, Lysichiton Kamtschatcensis, Acer gla- 

 bmm, Holodiscus ariaefolvus, Ccanotlutft sanguineus, and Linnaea 

 borealis. Two forms of parasitic fungi are usually prevalent. 

 Tramctes pitii and Echinodontium tinctorium, the former at- 

 tacking the white pine, Douglas spruce, larch and some other 

 species, the latter found almost exclusively on the hemlock and 

 fir. 



The aspect of the forest is strongly mesophytic. Tender 

 leafy plants of more or less delicate structure, suited to a humid 

 forest and moist soil, evidence in all species of rapid and vig- 

 orous growth, and the attainment of extraordinary size, all point 

 to conditions exceptionally favorable. Acer glabrum elsewhere 

 a shrub of ten or fifteen feet, here becomes a tree, 30 feet or 

 more in height and in diameter 8 or 10 inches. The white 

 pine itself may attain 7 feet in diameter, the black cottonwood 

 (P. triehocarpa) 3 to 4 feet, the hemlocks 2 to 3 feet, and 

 other trees more or less. The forest floor is usually covered 

 with a litter of branches and leaves among fallen logs, support- 

 ing a growth of mosses and liverworts, while fleshy fungi of 

 many genera and species abound. Among the small plants may 

 also be found Pijrola aphylla, Pterospora Andromeda, Monotropa 

 uniflora, and Cdrallorrhiza multi-flora and other orchids and 

 plants more or less mycotrophic in habit. 



Forests of this sort are limited to relatively small areas in 



