iQig] VESTAL— PHYTOGEOGRA PHY OF COLORADO i6l 



meanders and oxbows in the streams, and there are in some parks 

 small lakes in morainal depressions. The stream-sides are fre- 

 quently boggy, with meadows adjoining. The parks are mostly 

 treeless, or nearly so, and show no signs of former or impending 

 forestation. The exposed dry fiats are covered with dry grass- 

 land, its composition depending on altitude and geographic position 

 chiefly. Differences in soil texture cause local variation of the 

 grassland, but this is less marked and less minutely local than on 

 the hill slopes. Certain lower areas are occupied by meadow and 

 sedge communities, and the rolling surfaces of moraines (in montane 

 parks) are variable in soil texture, soil moisture, and in the compo- 

 sition of their grassland cover; but the greater part of park floors 

 is well drained, flat, and quite uniformly covered with dr}- grass- 

 land. This vegetation, in any one park, forms what might be 

 called a crystallization of the grassland of the neighboring hills, 

 whether in foothills or montane zone, in view of the comparative 

 uniformity of the grassland of the flats as contrasted with that of 

 the diversified slopes of hill topography. The lower parks have 

 a grassland cover very like that of coarse soil in the mountain- 

 front area or in the plains (see description of Estes Park in the 

 regional section) . The higher parks have fewer plants of the plains 

 and more of the mountains. There is a floristic and vegetational 

 gradation from plains grassland through the lower parks to mon- 

 tane grassland as seen in the higher levels. The parks thus show 

 a steplike series of floristic and ecological changes with altitude. 

 Ramaley (id, ii) for some years has studied park vegetation, 

 especially in Boulder Park at Tolland, Colorado, on South Boulder 

 Creek. 



TRANSITION AREA OR MOUNTAIN-FRONT ZONE 



The sedimentary rocks, lying upon the granite, are upturned at 

 the monoclinal fold, and are seen in a horizontal series of exposures 

 of strata, the lower and older members abutting on the granitic 

 foothills to the west, the upper formations outcropping in order 

 toward the east. Since the tilting at the mountain-front is for 

 considerable distances greater than 45° (locally reaching 90° and 

 even more, resulting in overturns), the lower formations have 

 narrower zones of outcrop than the upper strata, which dip so 

 slightly as to cover areas many miles wide in the plains. The 



