290 JOHN ERNST WEAVER 



During the first week in May, four atmometers were placed 

 in the prairie formation on Kamiak Butte and two in the same 

 formation at Viola. Owing to accidents and the loss of some 

 readings, complete data from only four instruments were obtained. 

 The two sets of readings from the Kamiak atmometers, which 

 were placed only a few meters below the pine zone, are shown 

 combined in figure 7. The rainfall on the chart in this figure is 

 given in cm. for a station near Viola at an altitude of approxi- 

 mately 1000 m. The readings of the Viola atmometers (not 

 shown here, but combined with those from Kamiak in fig. 9) 

 were very s'milar. 



Just within the edge of the pine zone and 20 m. above station 

 No. 7, station No. 8 was maintained. Here the ground is covered 

 with pine needles which almost exclude undergrowth and the 

 atmometer was shaded only indifferently by the open growth 

 of the trees. That this was a decidedly xerophytic habitat is 

 shown by the evaporation graph (fig. 7, graph 1) which closely 

 follows that of the prairie. The evaporation data in the more 

 typical yellow pine habitat located on the northwest slope of 

 the butte at Viola is plotted on the same chart for sake of com- 

 parison (fig. 7, graph 2). 



Station No. 9 was located on the north side of Kamiak 

 butte nearly opposite No. 7 and No. 8, about 20 m. from the top, 

 in the fir-tamarack association. The mountain side having 

 been cut over about 35 years ago, the trees of this association 

 are chiefly second growth. Douglas fir and tamarack are nearly 

 equally distributed with a mixture of about 3% white fir. The 

 pines are almost excluded. The chief shrubs of the undergrowth 

 are Rubus parviflorus, Rosa gymnocarpa, Pachistima myrsinites, 

 Vaccinium macrophyllum, and half-dead bushes of Opulaster 

 pauciflorus. Other important plants of the undergrowth are 

 Linnaea americana. Arnica cordifolia, Vagnera amplexicaulis, 

 Anemone quinquefolia, Calamagrostis suksdorfii, Cytherea bul- 

 bosa, and Fragaria platypetala. In most places the undergrowth 

 is poorly developed and often the forest floor is nearly bare. 



The station in the fir-tamarack association at Viola was 

 located two-thirds of the way down the northeast slope of the 



