SCIENTIFIC EXPEDITION TO NORTHWESTERN COLORADO 



II 9 



may be seen occasionally. Quercus gunnisonii, Amelanchier oreophila 

 and Rhus trilobata are usually abundant, sometimes growing even 

 within the stream-bed. The roots of these shrubs are often exposed 

 along the eroded sides of the bank. Flood plains of the intermittent 

 streams consist of soil rich in alkali and are usually covered with grease- 

 wood (Sarcobatus vermiculatus) . 



Vegetation of streamside and gulch. — At an altitude of 7,000 feet, 

 the streamside vegetation differs considerably from that at lower eleva- 

 tions. This is due partly to the direct effect of climatic differences 

 which accompany a change of altitude, but in great measure to differ- 

 ences of stream topography. At lower elevations there are large, 

 meandering streams flowing in wide valleys, which give an abundance 

 of bottom-lands with a deep and fine-grained soil. In the lower foothills, 

 on the other hand, there are many small streams; these, as well as the 

 large ones, flow in narrow and steep-sided gulches. Thus in addition to 

 streamside moisture, exposure must be considered as an important 

 factor. Moist, shaded slopes and gulches have their characteristic 

 forms of plant life. Hence in the lower foothills we shall speak of 

 streamside and gulch vegetation rather than of streamside and bottom- 

 land vegetation. In the following list particular notice should be called 

 to such typical gulch forms as Populus tremuloides, Pseudotsuga mucro- 

 nata, Vagnera stellata, Sidalcea Candida, Sidalcea neo-mexicana, Geranium 

 richardsonii, Acer glabrum, Angelica ampla, Lonicera involucrata and 

 Actaea viridi flora. The two species of Sidalcea occur in great abun- 

 dance and are invariably found growing together. 



Collection of Streamside and Gulch Plants 



Equisetum arvense L. 



Picea parryana (Andree) Sarg. 



Pseudotsuga mucronata (Raf.) Sudw. 



Elymus condensatus Presl. 



Hordeum nodosum L. 



Scirpus lacustris L. 



Juncus saximontanus A. Nels. 



Allium cernuum Roth. 



Vagnera amplexicaulis (Nutt.) Morong 



Iris missouriensis Nutt. 



Populus angustijolia James 



Populus tremuloides Michx. 



Salix spp. 



Alnus tenuifolia Nutt. 



Betula fontinalis Sarg. 



Quercus gunnisonii (Torr.) Rydb. 



Urtica gracilis Ait. 



Eriogonum campanulatum Nutt. 



Eriogonum umbellatum Torr. 



Eriogonum umbelliferum Sma'l 



Polygonum spergulariaeforme Meis. ( ?) 



Rumex occidentalis Wats. 



