THE FOOTHILL VEGETATION 103 



young- growth of Pseudotsuga taxi folia, Larix accident alis and 

 Pinus monticola, and the northeastern slopes on which no re- 

 forestation had taken place, but which were occupied by a low 

 and scattering stand of Ceanothus velutinus. 



That the slopes at Haugan were originally forested by the 

 slow process of conquest which seems to be the rule where the 

 pines invade the prairie is of course impossible to say, but that 

 transitions occur from the grassland to an open pine forest, and 

 then to the full occupation by Douglas spruce, larch and other 

 species, has been pointed out in the case of the forests of the 

 Flathead Valley (73), and apparently is of common occurrence 

 elsewhere. 



The severity of the conditions on an exposed western slope 

 is not at first evident. Such slopes are usually covered with 

 tall waving bunchgrass. Agropyron spicatum, and a host of 

 herbaceous, plants mostly perennials, among which the following 

 are conspicuous : 



Balsamorrhiza sagittata Cogswcllia macrocarpa 



Senecio canus CogsweUia simplex 



Monarda menthae folia Pentstemon Wilcoxii 



Delphinium bicolor Arabis Nnttallii 



Zygadenus venenosus Comandra pallida 



Mertensia oblongi folia Woodsia scopulina 



CogsweUia montana Selaginella densa 



Achillea lanulosa Lupinus ornatus 



Clarkia pulchetta 



The active vegetative period of most of these plants comes 

 early in the season before the rains have ceased, and by the 

 middle or the end of July they have finished fruiting. The test 

 of the season comes during July and August, when scant pre- 

 cipitation, high temperatures, clear skies and dry winds draw 

 from the thin soil almost its last vestige of moisture. Such con- 

 ditions are impossible for forest trees, except- where the seedling 

 is sheltered in the lee of some rock or in the bottom of a gully. 

 Xow and then on such slopes a single yellow pine has rooted and 

 grown to large size where one chance in millions has placed a 

 seed in favorable conditions. 



A series of experimental operations conducted to determine 

 the practicability of forest planting on sites of this character, 



