1906] SHANTZ—VEGETATION OF THE MESA 43 
Muhlenbergia gracillima consocies—This consocies covers the 
greater part of the lower land, particularly that south of the Mesa. 
The following quadrat is typical. 
Muhlenbergia gracillima....... 46% ~ Boebera ‘papposi.. os 27. 25 
Schedonnardus paniculatus...:; 6% Plantago Purshii.::..:...)2..7.0%4 9 
Bouteloua oligostachya........ 1% » Senecio oblanceolatits..2). 205.5714 I 
Artemisia frigida......... 19 1.5% Hedeoma nanes....5.1.433 ee I 
Munroa SQUAFTOSA SS .).  sev I Salvia: lancedlate.;.<22 05.2 ~ oe I 
Gutierrezia Sarothrae..... 9 Euphorbia glyptosperma........... I 
Picradeniopsis oppositifolia 3 otal surface covered........... 56% 
Water content: vernal period 9-14%; aestival 7-9%; autumnal 5~-7%. 
Soil, loam. 
This consocies should also show Opuntia polyacantha, Stipa 
Vaseyi, Argemone intermedia, Senecio spartioides, Verbena brac- 
‘eosa, Atriplex argentea, Malvastrum coccineum, Astragalus cras- 
sicarpus, A. bisulcatus, Sophora sericea, Quinculata lobata, Agropy- 
ron occidentale, and many others. 
In places M uhlenbergia gracillima is even more dominant 
than in the quadrat given above, but as one passes to the higher 
ground it gives way gradually to Bouteloua oligostachya. 
Bouteloua hirsuta consocies—This consocies is best developed 
on the crests and over the north portion of the Mesa. A quadrat 
best illustrates the structure. 
Bouteloua hirsuta.......... 95 17%  Sideranthus spinulosus.......-.-.. 7 
Artemisia frigida.......... 4%  Oreocarya thyrsiflora...........--- 6 
theropogon curtipendulus 1.5%  lLacinaria punctata.............--- 4 
Aristida longiseta..,....... 4 1% Gaura coctines......--°:--..--«-: 3 
Andropogon scoparius...... .5% Euphorbia robusta.......-.------- 2 
Bouteloua oligostachya.... . 3% necio MOR‘ CO isk os ts I 
Thelesperma gracile 2... 16 tragalus Shortianus........------ I 
Echinocereus viridiflorus 8 Pentstemon secundiflorus.......--- I 
Senecio oblanceolatus...... 7 Total surface covered......--- '. 32% 
Water content: vernal period 4.5-9%; aestival 2.5-4.5%; autumnal 1.5~ 
2.5%- Soil, coarse gravelly loam. This quadrat also illustrates the structure 
of the vernal Euphorbia robusta society. 
While Bouteloua hirsuta is predominant in this consocies, many 
other species are important. Muhlenbergia gracillima is sometimes 
Present; Aristida longiseta and Sitanion elymoides are sometimes 
