392 BOTANICAL GAZETTE [juNE 
to those enumerated in the blue-stem formation, are Helianthus 
petiolaris, Potentilla arguta, Argemone alba, Plantago Purshii, Linum 
rigidum, etc. 
The blowout formation is restricted to peculiar crateriform 
hollows formed by the action of the wind, and termed “blow- 
outs.” In its young and typical condition, it is the most open 
of all plains formations. It occurs, of course, only in the sand 
hills proper, since it is here only that blowouts are formed. The 
facies of the formation are Redfieldia flexuosa, Muhlenbergia 
pungens, Eragrostis trichodes, Oryzopsis cuspidata, and Calamovilfa 
longifolia. The colonization of a recently formed blowout is 
brought about by means of Redfieldia flexuosa, which is uniformly 
the first grass to make its appearance in these hollows of shift- 
ing sand. The slight stability imparted to the sand by it 
enables Muhlenbergia pungens and Eragrostis trichodes to secure a 
foothold. These are followed by other grasses, and then by such 
secondary species as Tradescantia Virginica, Eriogonum annuum, 
Meriolix serrulata, Lathyrus ornatus flavescens, Phaca longifolia, and 
Euphorbia petaloidea. By this time the sand of the blowout has 
ceased to shift, and a host of ordinary sand hill inhabitants 
appear, resulting in the complete reclamation of the blowout and 
the decadence of the formation which characterized it. The 
process of reclaiming a blowout is very gradual, and the period 
between the incipience and the decadence of sucha formation 1s 
often as much as ten years. 
The sand draw formation has much in common with the 
- blowout formation. It is less frequent, however, and is not so 
well characterized. Oddly, the grasses are not the control- 
ling species. Their place is taken by Cristatella Jamesi, and 
Polanisia trachysperma. In a typical sand draw, the grasses 
are represented only by scattered tufts of Munroa pi henlte 
Eragrostis major, Sieglingia purpurea, and Paspalum setaceum. ? 
most frequent secondary species are Euphorbia petaloidea, L- 
hexagona and E. montana. 
The foothill formations are three, 
(1) the undershrub 
formation of table lands and bad lands, (2) the mat and rosette 
