280 BOTANICAL GAZETTE [ocroBER 
xerophytic relict along the crest of prairie knolls, where it mingles 
with the gramas as they advance upon the bunch-grass stage, yet 
usually as a secondary element among these sod-formers. In our 
area, however, it is lacking. 
Bouteloua hirsuta seems to be the pioneer of the gramas as they 
encroach upon Bulbilis, or upon the bunch-grasses where Bubbilis 
is absent, as is the case in our formation. It is in turn apparently 
C. Solidago 
rigida to the left; Helianthus scaberrimus to the right; admixture in the background. 
1.—Serotinal aspect: Bouteloua curtipendula sod on upper slope; 
followed by B. oligostachya, which seems to occur more abundantly 
and to occupy the most prominent place of the sod-formers. sd 
quently it alone encroaches upon the bunch-grasses, B. hirsuta bene 
absent. Next comes B. curtipendula (fig. 1), which also contributes 
largely to the early prairie sod. In many places the Poa sod is al 
next to follow. The gramas are thus largely confined to the a 
decreasing in abundance downward, where they not infrequently 
rise to facial prominence. Contrary to the serotinal floral —_— 
the Boutelouas are of low stature, B. curtipendula alone rising above 
