46 BOTANICAL GAZETTE [yoy 
> 
the clay flats it often gives way to the M uhlenbergia gracillima or 
A gropyron occidentale consocies, and in passing to sandy or gravelly 
ridges it is often dominated by the Bouteloua hirsuta, Andropogon 
scoparius, or Koeleria cristata consocies. Even on the slopes of 
more level sandy areas it alternates with the Calamovilja longt 
jolia consocies, and at times with the Andropogon furcatus con- 
socies. Although these consocies dominate immense areas, they 
are not to be regarded as constituting distinct formations. Boule 
loua oligostacyha is prominent everywhere and these are merely 
modifications of the Bouteloua formation, or in other words, con 
socies of this formation. 
To discuss each aspect of this formation would take too much 
space, and some idea may be obtained by referring to the lists given 
earlier in this paper. 
There is a rather marked zonation in regions characterized by 
rolling or uneven ground. The hills and ridges are occupied by 
Bouteloua hirsuta. Jn this habitat there is a rather marked alternation 
with other consocies. Andropogon scoparius often becomes domi- 
nant, as does also Koeleria cristata. Here are also found a numbet 
of prominent societies, among which the most xerophytic is the 
Selaginella densa society. S porobulus crypiandrus and Stipa comata 
may also become prominent. 
Occupying the sides cf the slopes and the level expanses is the 
extensive Bouteloua oligostachya consocies. Alternating with this 1s 
found the Andropogon jurcatus and the Calamovilja longifolia con- 
socies. This alternation is often very marked, the consocies remain 
ing distinct from each other. 
It is here that the most important societies of the formation are 
found, many of which extend for many miles without interruption- 
Among the most prominent of these societies is the Grindelia squar — 
rosa society, which extends for many miles east of Limon, Col. 
and occurs over less extensive areas in many other parts of the forma 
tion. The Schedonnardus paniculatus so 
Col., and Goodland, Kans. 
of the most prominent so 
ciety occurs throughout the | 
formation and in many places is very extensive. Between Burlington, — 
» the scciety extends for many miles: — 
Thelesperma intermedium also occurs in this consocies. It is one — 
a Ee ee a 
cieties in the formation and is especially e 
