2904 BOTANICAL GAZETTE [OCTOBER 
extends up to and even dominates the prevernal and vernal floral 
aspects. 
Summary of the structure of the formation 
The formation is strictly of the prairie-grass type, its facies being 
determined mainly by six species: Bouteloua oligostachya, B. curti- 
pendula, B. hirsuta, Koeleria cristata, Andropogon furcatus, and A. 
scoparius, to which must be added Poa pratensis in valleys and on 
lower slopes. The Andropogons are the main sod-formers of crests 
and ridges, while the Boutelouas characterize the higher slopes, 
working up to the crest and ridges. Koeleria seems to be more 
closely associated with the Boutelouas, occurring on middle slopes 
mainly. With these are associated three sedges and seven other 
grasses, which are all important as cooperating sod-formers, some of 
them ranking as primary species in the formation. We may mention 
Carex pennsylvanica, C. festucacea, and Sporobolus brevifolius as 
perhaps the more important of these. It is to be remarked that the 
sedges are all pre-estival, while the grasses are all estival or pee 
estival in their floral activity; the first facies to bloom is Koeleria 10 
the estival aspect, while the Boutelouas are serotinal and the Andro- 
pogons autumnal. 
Upon this facial background of grasses there progressively appe™ 
several conspicuous flowered forms of primary importance, which 
with numerous secondary and tertiary species serve to impart 4 
bizarre aspect to the formation when considered as @ whole and 4 
: x ‘ ‘ z . ns 0 
kaleidoscopic shift with seasonal succession. In passing it 1s oe 
note that species primary in their own floral aspect may Lagogies y 
consider 
secondary or tertiary importance when the formation is con ae 
as a unit. Among these primary species we may note the ubiqu 
Aniennaria campestris; the Spesias and Sisyrinchium ©! seibid 
slopes; Amorpha canescens upon upper slopes and sauce pre 
T , 
upon lower, and Verbena and Erigeron ramosus upon upper » se 
Symphoricarpus in valleys and on lowest slopes; the eae K. 
upon slopes, K. purpurea occupying the upper slopes, ps ee 
candida extends downward upon lower slopes; Solidago rigida 
Helianthus scaberrimus of great frequency and abundance; and 
Aster sericeus upon isolated knolls. 
