Prairie- and Sand Hill District. 527 
Prairie Grass Formation‘). The principal grasses of this formation are 
sod producers and the soil is therefore covered with a close turf. The facies 
are Sporobolus asperifolius, Koeleria cristata, Eatonia obtusata and Panicum 
Sceribnerianum. In different localities plants of adjacent formations wander in 
and modify the constitution of the formation. For example Stipa spartea and 
Panicum virgatum enter from the meadow formation, Aristida purpurea from 
the beard-grass formation and Buchloe (Bulbilis) dactyloides from the buffalo- 
grass formation. Bouteloua curtipendula and B. oligostachya are important 
secondary species of great frequency here, as in all the grass formations. 
Andropogon scoparius and A. furcatus which are characteristic of certain other 
formations are of comparatively little abundance. Agropyrum pseudorepens, 
in low prairies becomes a bunch-grass. The important secondary species, 
however, are Festuca ovina, Eragrostis pectinacea, Sporobolus asper, S. vagini- 
Rorus, Agrostis hiemalis and Schedonnardus paniculatus. 
vernal and an estival-serotinal ur fäie ERiee eg POUND and CLEMENTS, are pr resented 
‘by this formation. The grassy covering in the spring is spangled with Draba caroliniana, An- 
drosace Scrideniali, Sceutellaria parvula, Astragalus crassicarpus (= A. caryo ee Antennaria 
campestris, Peucedanum Teilen, Carex menden Fe bracteata, caro- 
liniana, Comandra umbellata, On low prairies je rnal species are Allium muta er "Callirh 
alcaeoides, C. Ernn Lithospermum eg = L. ER and Viola aaa 
In the autumn, the prairie is brightened by Amorpha species of Solidago, Verbena, ae 
Aster, Liatris. En e of the grasses the most characteristic plants are Amorpha escens, 
Psoralea floribunda, ER rigida, S. rupestris, S. canadensis, S. rigidiuscula, S. gr Ver- 
bena stricta, V. hastata, Kuhnistera purpurea, K. candida, Liatris scariosa, L. punctata, L. squar- 
rosa, Aster multiflorus, A. sericeus and Vernonia gigantea (= V. altissima). These are Bine of 
greater frequence. The widely distributed and scattered plants are: Cnicus (Carduus) undulatus, 
Achillea millefolium, Messdenia (Cacalia) tuberosa, Prenanthes (Nabalus) en Gerardia purpurea, 
Potentilla arguta ile rpum spinulosum, Hymenopappus flavescens, Yucca angustifolia 
(= Y. glauca), Cactus viviparus, Opuntia missouriensis (= O0. te Evolvulus pilosus, 
and Talinum teretifolium are all common. 
HARVEY) has traced a similar succession of plant species on the prairies 
of southeastern South Dakota 
The prevernal aspect is due to the flowering of Antennaria campestris, Carex pennsyl- 
vanica, Peucedanum nudicaule, Pulsatilla hirsutissima, as principal species, together with Astra- 
galus crassicarpus, en foenieulaceum, Draba micrantha, and Ranunculus ovalis without 
these euer contributing to the formation of a facies. The vernal a. begins with the 
blossoming of Troximon (Noth alas euspidatum Bu en angustifolium (= L. lineari- 
folium), sh followed by Castilleja sessiliflora, Lithospermum canescens, Viola pedatihda and 
Oxalis violacea, Pass . Gaura coccinea, Psoralea an the last two ending the 
vernal period about the first of Jun 
estival aspect is lt by decided Ba changes and flowering of Panicum 
RE | Koeleria cristata, Rosa arkansana, Eri ramosus, Delphinium carolinianum 
(= D. azureum) and Brauneria pallida. The Beet is feinen by Koeleria cristata, Poa pratensis. 
ı) Pounp, RoSCoE and CLEMENTS, FREDERIC, E.: The Phytogeography of Nebraska 1900: 
348 et seq.; also THORNBER, JOHN, J.: The prairie-grass Formation in Region I. Botanical 
Survey of Nebraska V (1901); 29—143. 
2) Harvey, Botanical Gazette XLVI: 277—298, Oct. 1908. 
