1906] SHANTZ—VEGETATION OF THE MESA 195 
apetalum,Polygonum aviculare, Artemisia frigida, A. canadensis, 
Verbena bracteosa, and Plantago Purshii; while farther back were 
found Bouteloua oligostachya, Schedonnardus paniculatus, Chrysop- 
sis villosa, Arenaria Fendleri, Gilia aggregata, G. pinnatifida, Senecio 
oblanceolatus, Gutierrezia Sarothrae, Koeleria cristata, and Sitanion 
elymoides; followed by the Bouteloua formation in which Bouteloua 
oligostachya, Stipa comata, and Arenaria Fendleri were most 
important, 
The stages of a succession which converts a denuded trail into 
the Bouteloua formation are not marked. First there is, as a rule, the 
entry of many annual ruderal species (fig 12). This in many cases is 
followed by Stipa Vaseyi, followed by Schedonnardus paniculatus, 
Sitanion elymoides, and Aristida longiseta, as well as many other 
secondary species of the formation, and these in turn by the facies 
of the grass formation. In some places Stipa Vaseyi does not enter 
and here may be found many other species. Among the more 
important are Schedonnardus paniculatus, Gutierrezia Sarothrae, 
Chrysopsis villosa, Artemisia frigida, A. canadensis, and many 
other species, followed by the facies of the grass formation. 
Near Cheyenne Mountain a number of abandoned corrals show 
the following as the most important invading species: Schedon- 
nardus paniculatus, Artemisia canadensis, Solidago sp., Artemisia 
jrigida, A, gnaphalodes, and a number of secondary species— 
Petalostemon purpureus, Thelesperma gracile, Chrysopsis villosa, 
Pulsatilla hirsutissima, Lacinaria punctata, Sporobolus cryptandrus, 
Aristida longiseta, Bouteloua hirsuta, Aragallus Lambertii, and the 
Tuderals Boebera papposa and Euphorbia glyptos perma, 
A denuded quadrat showed during the third summer Artemisia 
canadensis, Geranium caes pitosum, Pulsatilla hirsutissima, Chrysopsts 
villosa, and Artemisia Iudoviciana. A second corral showed 
Artemisia canadensis and A. jrigida as the chief invaders, with many 
other species coming in, of which those most important are Schedon- 
nardus paniculatus, Bouteloua oligostachya, and Koeleria cristata. 
The early stages of these successions vary greatly. In the study 
of a large number the following plants are found to enter first: 
Boebera pap posa, in the mesa region and adjacent areas; northward 
toward Palmer Lake, Plantago Purshii or Polygonum aviculare; 
