1906} sHANTZ—VEGETATION OF THE MESA 47 
well developed just east of Colorado Springs. The Gutierrezia 
Sarothrae society occurs more often near the mountains and bluffs. 
Artemisia canadensis is also important in similar locations, while 
A. dracunculoides is most abundant farther out on the plains. Opun- 
tia polyacantha in most places merely forms small communities or 
families, but in many places on the plains these become associated 
into an extensive society. This is especially true east and south 
of Fountain, Col. O. arborescens is also found in this region and 
extends northward to within a few miles of Colorado Springs. 
Carex stenophylla, Senecio oblanceolatus, Sophora sericea, Astra- 
galus Drummondii, Oreocarya suffruticosa, Eriogonum annuum, 
Chrysopsis villosa, Boebera papposa, and Plantago Purshii each 
form extensive societies in this consocies. The following s<cieties 
are not so extensive, but on account of the prominence of the plants 
characterizing them they are very noticeable: Ipomoea leptophylla, 
Yucca glauca, Lupinus argenteus, Carduus plattensis, Eriogonum 
effusum, Chrysothamnus graveolens, Senecio spartioides, Pentstemon 
angustijolius, P. secundiflorus, and Astragalus bisulcatus. 
Passing now to the lowlands, the Bouteloua oligostachya ccn- 
socies is found with very few primary or secondary species, and 
usually alternating with the Muhlenbergia gracillima and the Agro- 
byron occidentale consocies. These consocies are sometimes mixed, 
but as a rule remain distinct. A gropyron occidentale, a tall slender 
8tass, is usually not associated with many other species, and the 
mats of Muhlenbergia gracillima also leave little space for the develop- 
ment of any but a few of the clay-loving annuals. Astragalus 
bisulcatus, Sophora sericea, Boebera papposa, Plantago Purshii, and 
Atriplex argentea are among the most important secondary species 
of these consocies. 
UNIVERSITY oF Missouri, 
Columbia, Mo. 
