1917} VESTAL—FOOTHILLS VEGETATION 379 
Herbs 
Pteridium aquilinum Fragaria OE et spp. 
Smilacina stellata (ch) Aralia nudicauli 
Smilacina amplexicaulis (ch) Viola ade Rydbergii (ch) 
Stellaria Jamesiana astilleja miniata et s 
Thalictrum spp. Monarda Ramaleyi et spp. 
Aquilegia coloradensis Hydrophyllum Fendleri (ch) 
Delphinium Nelsonii (ch) Galium boreale (ch) 
Ligusticum Porteri (?) Galium aparine 
Saxifraga rhomboidea (ch) Galium Vaillantii 
The canyon forest presents a wide range of variability, according 
as favorable ground conditions are uniform or interrupted; thus 
in rocky canyon-bottoms and slopes it is patchy in development. 
It may merge into, or mingle with, areas of Pseudotsuga, mixed 
shrub, aspen, Populus-Salix, Quercus, and moist grassland growths. 
The herbs especially may be no more typical of unmixed meso- 
phytic deciduous forest than of many other mesophytic habitats. 
The characteristic plants growing in the shade of large shrubs and 
trees are Viola, Hydrophyllum, and one or more species of Galiwm. 
These are abundant in unmixed canyon forest, at least in the 
northern foothills. 
Amelanchier is an important component only in the upper foothills and the 
montane zone, or farther north and west in the Rocky Mountains. Acer 
glabrum often occurs by itself on north or shaded slopes, the bushy plants 
10-15 ft. in height, and in most places considerably separated. Prunus 
demissa, and several species of Crataegus (mostly C. coloradensis and C. cer- 
ronis), together or singly, dominate tall thickets or low forests, which may be 
regarded as transitional cnapbabaniae te mixed shrub and canyon forest associa- 
tions. In new growths or they are low and scrubby; in other 
places they form a taller and ‘closed growth, with a lower stratum of mesophytic 
herbs, and may properly be spoken of as forest. Prunus demissa and Crataegus 
form relatively much more extensive areas of vegetation in the northern foot- 
hills and especially along the northern mountain-front than in the southern part 
of Colorado. Robinia is abundant in the southern third of the foothills area. 
It ranges into drier habitats, in which it is low and scrubby. 
The Alnus-Betula consocies has been mentioned as being abundant along 
mesophytic stream-sides. Corylus is frequent only in such situations, occurring 
in places alone, in others with Alnus and Betula. The climbers, clematis, 
Virginia creeper, and grape, are local, and more common in sunny openings. 
Viburnum is in moist canyon-bottoms of the higher foothills. 
