292 JOHN ERNST WEAVER 



butte on the side opposite the station in the prairie. Here, as 

 at Kamiak, the forest is second growth. Actual count showed 

 the trees to be mostly 32 years old. They are principally Douglas 

 fir and tamarack, among which the Western cedar (Thuja plicata) 

 is coming in, while the numerous dead yellow pines tell the story 

 of the lost struggle for light. The rather sparse undergrowth 

 is very similar to that in the fir-tamarack forest on Kamiak 

 Butte. The graph representing evaporation here corresponds 

 in general with that obtained at Kamiak (fig. 7) and like it 

 shows without exception a continuous lower daily rate of evapor- 

 ation than that in the pine association. All the graphs plotted 

 show three periods of extreme evaporation, one in early June, 

 another in late July and the first week in August, and still another 

 the last week in August. At the time of the second maximum, 

 the prairie and pine soils at both Kamiak and Viola had lost 

 all of their available water to a depth of 25 cm., while in each of 

 the two fir-tamarack stations a margin of only about 12% above 

 the nonavailable point was left on July 24. 



Thatuna Hills extend southeast from Viola and reach their 

 culmination in Cedar Mountain, a point about 1500 m. high, 

 lying eighteen miles east of Pullman. Here we find in the cedar 

 association the climax type of forest of the region. On June 14, 

 as soon as the snow had melted away, stations were established 

 on the north slopes of this mountain about 200 m. from the 

 summit, one in the cedars and one over a ridge about 250 m. 

 eastward in the fir-tamarack association. 



The cedar association (station No. 10) occupies a north slope 

 and a ravine, through which flows a small stream. This forest is 

 over 95% pure cedar, mostly large trees from 70 cm. to more 

 than a meter in diameter (fig. 8) while the rest of the trees are 

 large white firs which are mostly dead. Near the stream the forest 

 floor is covered with Athyrium cyclosorum which gives way further 

 back to a rather dense growth of Rubus parvifloi'us, Vagnera am- 

 plexicaulis, Tiarella unifoliata, Trillium ovatum, Clintonia uniflora, 

 Disporum majus, Pyrola spp, Actaea spicata arguta, and Coptis 

 occidentalis. These with Viola spp., and Streptopus amplexi- 

 folius together with Phegopteris dryopieris, and the seedlings of 



