LICHENS OF THE STATE OF WASHINGTON 3 



bark. Under proper environmental conditions these will grow into mature 

 lichens, of the same species that produced them. Some species have never 

 been found bearing fruit-bodies, so they must be reproduced either by 

 soredia or fragmentation. It is known that fragmentation is a common type 

 of multiplication of many kinds of lichens. Rejuvenescence takes place in a 

 number of lichens, but it is especially noticeable in specimens of crustose 

 and foliose forms, in which the center of the thallus mat has died and the 

 periphery has remained alive. Here there may be seen new centers of growth 

 arising at various points. This enables a single lichen to spread a consider- 

 able distance over the substratum. Rejuvenescence also takes place in the 

 Cladonias, in which the basal portions of the podetia die and growth con- 

 tinues at the tops of the podetia. 



The lichen flora of Washington represents a wide variety of forms, no 

 doubt a result of the varied and interesting topography of the state. The 

 Cascade Mountains divide Washington into an eastern and a western section. 

 The western section, which comprises three-eighths of the state, consists of 

 the Pacific Coastal Plain, the Olympic Mountains, and the Puget Sound 

 Basin. Land elevations vary from sea level to an average of 6000 feet for 

 the Cascades and nearly the same for the Olympics. Several peaks in the 

 Cascades have an elevation of over 10,000 feet, while Mt. Rainier, the high- 

 est in Washington, is 14,408 feet. Both the Olympics and the Cascades 

 have a great efifect on many of the physiographic features of the state ; how- 

 ever, the Japanese current is largely responsible for the mild temperatures 

 on the ocean side of the Cascades. The prevailing winds which are from 

 the ocean bring to this western section a marine climate characterized by 

 considerable moisture, cool summers and comparatively mild winters. These 

 moisture-laden winds, from the ocean, must first rise to pass over the 

 Olympics and later over the Cascades ; hence the precipitation is heavy on 

 the windward slopes. Stations at sea level, on the windward side of the 

 Olympics, have an average precipitation of 125 inches, and those on the 

 leeward side less than twenty inches. The eastern section, comprising five- 

 eighths of the state, is all a part of the Columbia River Basin. In the north- 

 east are the Okanogan Highlands, consisting of gently rolling hills, with a 

 north and south trend, and an average elevation of 2000 feet, with some 

 peaks rising to 6000 feet. In the extreme southeast are the Blue Mountains. 

 Here the highest elevations are about 7000 feet. Since the prevailing winds 

 that blow across the state come from the west and southwest, the air has 

 lost most of its moisture after it has passed over both the Olympics and 

 Cascades ; consequently the air over all eastern Washington is dry most of 

 the year. Here the precipitation varies from an annual average of six inches, 

 in the lowest valleys, to more than sixty inches on the higher eastern slopes 

 of the Cascades. In some of the central valleys, such as Wenatchee and 

 Yakima, and also in the Great Bend Country and the Grand Coulee semi- 

 desert conditions prevail. For further information concerning the topog- 

 raphy or physical framework of Washington the reader should consult 

 Piper (1906), Martin and Corbin (1930), and Freeman and Martin 

 (1942). 



