1906] SHANTZ—VEGETATION OF THE MESA 197 
1904 covered the bank chiefly with Stanleya glauca and Mentzelia 
decapetala. A great deal of the soil of this bank was hauled in from 
the lime ridge region, and with it, the seeds of Stanleya glauca were 
carried in. In one of the other reservoirs, which is several years 
older, Medicago sativa was predominant. Normally, Boebera 
papposa, Stipa Vaseyi, and other ruderals would be expected to 
appear first. 
A new reservoir constructed on the mesa in 1904 showed during 
1905 the following species: Boebera papposa, Salsola Tragus, Senecio 
spartioides, Artemisia frigida, Senecio oblanceolatus, Argemone inter- 
media, Menizelia nuda, Polygonum aviculare, P. Douglasii, Euphor- 
bia robusta, Yucca glauca, Chenopodium album, Gaura coccinea, 
Cleome serrulata, Petalostemon purpureus, Amaranthus blitiodes, and 
A, retroflexus. 
In building roads and reservoirs it often happens that several 
meters of surface soil and all the vegetation is removed. Succession 
is different here from the places already mentioned. The annual 
ruderals.do not appear in such great numbers. Among the species 
which enter are Argemone intermedia, Mentzelia ornata, Petalostemon 
oligophyllus, P. purpureus, Sitanion elymoides, Aristida longiseta, 
Munroa squarrosa, and other common hillside plants, since the soil 
here is usually gravel. 
Broken areas. 
Here and there on the plains are found areas which have been 
plowed and planted, but have been abandoned because of the scanty 
water supply. The succession of plants here is much the same as 
on graded roads, but is usually more uniform. An abandoned 
garden patch showed the following year the facies Anogra albicaulis, 
with Chenopodium album and Helianthus annuus as the principal 
species. An area on top of the mesa showed almost a pure stand of 
Boebera Papposa; while still another showed Schedonnardus panic- 
wlatus. Artemisia frigida sometimes enters denuded areas and 
dominates the early stages of the succession. During 1904 a tract 
was seeded with Lolium perenne; the following summer it showed 
Boebera papposa and Verbena bracteosa, as well as Polygonum 
aviculare, Salsola Tragus, Artemisia frigida, Lolium perenne, 
