320 University of California Publications in Zoology [Vol. 16 



(Taj:us hrevifolia), western larch {Larix occidentalis), cottouwood 

 {Popiilus trichocarpa) , and birches {Betula microphylla) . A few 

 Englemann spruces {Picea Englemanni) occur and one silver pine 

 {Pinus monticola) was seen. There is a small amount of underbrush, 

 composed chiefly of dwarf maples {Acer glahrum) and alders (Alnus 

 sp.). The lowland-fir type of forest occurs only in the bottoms of deep 

 eaiions and in very damp places, and does not extend up on the moun- 

 tain slopes. 



On sheltered lower slopes the western larch and Douglas spruce 

 make up the larger part of the forest. Sometimes one and sometimes 

 the other is dominant. The larch is best developed in damp situations, 

 while the Douglas spruce covers drier slopes. Near Hompeg Falls the 

 larch-Douglas spruce forest occupies the north slopes of the side 

 ravines which branch from the main canon. The larch largely occupies 

 the bottoms of the ravines, while the Douglas spruce extends further 

 up the sides, and towards the tops of the ridges spreads out to form 

 a more extended forest. The Douglas spruce forest is usually fairly 

 dense in this situation and many of the slopes which it covers are very 

 steep. Under the heaviest forest of this kind there is no underbrush, 

 but the ground is entirely covered by dead needles. In other places 

 the forest is more open and more or less brush occurs, in which the 

 alder (Alnus sp.) is the most abundant type. The larch forest is more 

 open and usually does not have a heavy growth of underbrush. 



Along Butte Creek, where the bottom of the narrow caiion has 

 been much washed over by the stream, much of the lowland-fir forest 

 has been washed out and is replaced in patches by a deciduous forest 

 which is notable for the thickness of the underbrush. The dominant 

 trees are cottouwood [Popiilus trichocarpa) and the willows (Salix). 

 The brush was composed principally of alder (Alnus sp.), thoim 

 (Crataegus irevispina) , service-berry (Amelanchier florida), wild 

 cherry (Prunus demissa), red osier (Cormis stolonifera), dwarf maple 

 (Acer glahrum) , and snowberry (Symphoricarpus) . 



Traps set in the lowland-fir habitat near Hompeg Palls on July 23, 

 25, and 26, 1914, caught 1 Sorex vagrans dohsoni, 23 Peromyscus 

 maniculatus ganihelii, 1 Evotomys gapperi saturatus, and 2 Eutamias 

 amoenus amoenus from a total of 201 trap-nights. 



