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UNIVERSITY OF COLORADO STUDIES 



gonum tristichum is a successful herb of the shale slopes. Level areas 

 of shale soil are grown over with sage-brush. 



Ruderals. — The most common ruderal is sage-brush. With rabbit- 

 brush it forms the common roadside vegetation (Fig. 7). Russian 

 thistle is far less abundant than on the eastern plains. The following 

 is a list of some of the common ruderals : 



Chenopodium berlandieri Moq. 

 Salsola tragus L. 

 Vaccaria vaccaria (L.) Britton 

 Peritoma inornatum Greene 

 Peritoma serrulatum (Pursh) DC. 

 Melilotus alba Desv. 



Melilotus officinalis (L.) Lam. 



Orthocarpus luteus Nutt. 



Marmbium vulgare L. 



Aster hebecladus DC. 



Grindelia squarrosa (Pursh) Dunal 



A comparison of conditionseastandwestof the continental divide. 1 



— The general differences between the vegetation east and west of the 

 continental divide are very striking. These dissimilarities are more 

 marked in northern than in southern Colorado and at lower than at 

 higher altitudes. Comparisons may be made of climatic and vegetative 

 conditions at Rangely and Wray and at Boulder and Meeker. These 

 four stations all being near the 40th parallel, any effect of altitude is 

 eliminated (see map, Fig. 1, for relative locations). 



At Wray the vegetation is a grassland formation. This consists for 

 the most part of various bunch-grasses, of grama grass (Bouteloua 

 oligostachya) , and buffalo grass (Bulbilis dactyloides) At Rangely, 



1 Gray, Asa, and Hooker, Joseph D., "The Vegetation of the Rocky Mountain Region and a Com- 

 parison with That of Other Parts of the World," Bull. U. S. Geol. and Geog. Surv. of Territories," Vol. VI, 

 No. i, pp. 1-62, 1880. 



