Southeastern Washington and Adjacent Idaho. 89 



Galium sp. Viola glabella 



Streptopus ma jus Viola orbiculata 



Tiarella unifoliata Vagnera ample xicaulis 

 Trillium ovatum 



The high humus content and consequent great water holding 

 capacity of the soil is probably due in part to the lack of forest 

 fires. For it is easy to see how the more moist areas in the deep 

 ravines would be less subject to burning than the drier slopes 

 with their proportionally greater amount of undershrubs. The 

 forest floor supports the best developed fungus flora of the region. 

 This includes species previously enumerated. However, even 

 here the fungus flora is relatively scanty. 



Because of the shade the trees are often pruned high, while the 

 branches are draped with long strands of Usnea. Often at higher 

 altitudes Picea engelmanni accompanies the cedar down the moist 

 ravines but never assumes very great importance. 



The greater mesophytism and tolerance of the white fir as con- 

 trasted with that of the tamarack and Douglas fir are shown by the 

 presence of the former in the mixed cedar-white fir forest. It is 

 the last of these trees to give way to the cedar, certain communi- 

 ties showing gigantic relict white firs while all of the saplings are 

 those of the cedar. Proceeding up the slope from a cedar com- 

 munity the white firs become dominant as the cedars become 

 smaller and less frequent on the drier soil, then a zone of white 

 fir and tamarack is passed, while further up in this mixture 

 Douglas fir becomes more abundant. Of course, the illustration 

 is rather overdrawn for the accidents of windfalls, and especially 

 fires, may often greatly alter these conditions. 



The formation as a living developing entity has reached its 

 maturity in the cedar consociation. Because of the low light 

 intensity the establishment of the seedlings of the other forest 

 trees of the region in the cedar community is impossible. Hence, 

 the adult stage will go on indefinitely repeating itself generation 

 after generation, unless disturbed by some outside factor as a 

 forest fire or the hand of man. 



Having traced the normal development of the forest through the 



