STUDIES IN LAKE AND STREAMSIDE VEGETATION 155 



is compact, with a flora of its own, not made up merely of stragglers 

 from without. 



A total of 48 species is recorded in this zone. Of these, 68 per cent, 

 range to both lower and higher regions, while equal numbers (16 per 

 cent.) belong respectively to lower and higher altitudes (Table V). 



Forest Zone 



It may be somewhat misleading to speak of the forest as forming a 

 "zone." The forest is, in fact, the typical plant formation of the region. 

 At Redrock Lake, as elsewhere at the same altitude in northern Colorado, 

 the character of the forest depends much on slope and soil moisture. 

 In the wetter places, especially with north exposure, Engelmann spruce 

 forms almost a pure forest, with only some slight admixture of sub-alpine 

 fir (Abies lasiocarpa). The driest moraines and ridges support only the 

 limber pine (Pinus flexilis) . Places with intermediate conditions have 

 a mixture of trees, chiefly lodgepole (Pinus murrayana) and limber pine 

 and a few spruces and firs. 



To the south of Redrock Lake there is a steep glacial moraine, which 

 because of its slope to the north is cool and moist. Here is a dense 

 forest of Engelmann spruce. On the north the trees are chiefly limber 

 pines and lodgepole, the land here sloping gently to the lake at the 

 south. East of the lake where a full sweep of wind is possible direct 

 from the continental divide there is some typical "wind timber" forming 

 close, flat-topped masses of scrubby spruce and fir. These produce such 

 a dense shade that no plants except Polemonium will grow below. 



The herbaceous plants of the forest are naturally more numerous 

 than those of the other zones on account of the varied edaphic condi- 

 tions. Although the plants collected were all from within a hundred 

 meters (320 ft.) of the lake they are from dry and wet areas, open places 

 and shaded spots, soils containing humus and soil made of coarse, 

 disintegrated granite. On the whole, however, the forest may be con- 

 sidered xerophytic except where there are pure stands of Engelmann 

 spruce. The soil is dry and many of the plants exhibit the structures 

 looked for in dry-country species. The following are distinctly xero- 

 phytic: Aragallus spp., Lupinus, Astragalus, Antennaria, Sedum, 



