1906] SHANTZ—VEGETATION OF THE MESA 45 
Water content: vernal period, 6-12%; aestival 4-6%; autumnal 2-4%. 
Soil, coarse gravelly loam. 
This society belongs to the vernal aspect and alternates markedly 
with the above-mentioned society. So distinct is this alternation, 
that on adjacent crests these societies may occur with no mixing 
of the dominant species. It occupies the south and west crests of 
the Mesa. The species is widely distributed over the top of the 
Mesa, but seldom becomes dominant. 
The following quadrat is taken from a community of Leucolene 
ericoides: 
Leucolene ericoides.............. 78 Eriogonum Jamesii......----+--- I 
Bouteloua hirsuta................ 53 Psoralea tenuiflora........----+++ I 
Aristida longiseta................ 13. Allionia linearis.........+--+++-> I 
Eriogonum effusum.............. 3. Chenopodium leptophyllum ae aie I 
The Agropyron occidentale consocies is not as well developed in 
this region as elsewhere, but the following quadrat will show the 
structure. This quadrat is taken from a community of Bouteloua 
prostaia, 
Bouteloua prostrata.............. 352. Salvia lanceolata.....-.--+---++**- 11 
Agropyron occidentale............ 216 Polygonum aviculare....- S aicgee 10 
Bouteloua Oligostachya........... 47 Picradeniopsis oppositifolia.....-- 9 
Boebera an Se 123 Quincula lobata.....-----------° 4 
Verbesina encelioides............. 108 Salsola Tragus.....----+--++7+*° 2 
Gutierrezia Sarothrae............ 2 
3 — 
Water content: vernal period 13-17%; aestival 10-1 3%}; autumnal 8.5 
10%, Soil, clay. 
General discussion. 
While the vegetation of the Mesa is typical of the high plains, 
it does not show all of the structure that is at once apparent upon 
the examination of a larger area. On the Great Plains lying east, 
this formation is everywhere in evidence. By far the mest important 
species is Bouteloua oligostachya—the dominant species of the forma- 
tion. That part of the formation which is mest typical is the B. 
oligostachya consocies. This consocies is much more closed and 
pute on the great level plateau farther east than it is near the moun- 
‘tains. It often covers as much as 60-70 per cent. of the Saag 
and is associated with very few primary or secondary species. 41 
