STRTJCTUUE OF THE FORMATION 67 



THE LATE VEUNAL ASPECT 



Many of the plants of the early vernal period continue 

 throughout the late vernal aspect, so that this division is one 

 for convenience rather than otherwise. The facies of the 

 prairie formation are represented by three sod formers, 

 Panicum scribnerianum, Stipa spartea, and Koeleria cristata, 

 all of which occur throughout the prairie, but only in locali- 

 ties become of sufficient importance to rank as facies. Koe- 

 leria is most abundant on the higher slopes and crests of 

 ridges, Stipa and Panicum in the lower prairies and mead- 

 ows. Panicum averages twenty to twenty-five bunches per 

 quadrat, Stipa from five to fifteen, and Koeleria, when pres- 

 ent, twenty to twenty-five. Panicum is the first of the vernal 

 facies to blossom, closely followed by Koeleria and Stip<i. The 

 flowers of all are anemophilous and belong to the Longistam- 

 ineae; as would be expected, the stigmas are plumose and 

 exserted. Geaiiothtcs ovatus is a xerophytic shrub occupying 

 the exposed tops of the various ridges. Where most abun- 

 dant, it controls to a considerable extent the numbers of the 

 secondary species. Ceanothus occurs in every count made 

 upon the crest of Great ridge, ranging from three to twenty- 

 nine individuals to the quadrat. When we remember that a 

 single shrub of redroot contains from five to sixty woody 

 stems, some of which are branched, we get some idea of the 

 dominating influence it exerts. During May and the early 

 part of June, the crest of Great ridge is white with the in- 

 numerable panicled flowers of this plant. Two xerophytes, 

 Panicum pubescens and P. depauperatum, occur as small, 

 tufted perennials on Great ridge and some exposed slopes. 

 P- pubescens is the less abundant and is easily recognized by 

 its villous appearance and its smaller spikelets. Panicum de- 

 pauperatum is frequent, averaging about six bunches per 

 quadrat throughout its range. Neither of these grasses con- 

 tributes anything of note to the vegetative covering. Eatonia 



