1908] IITARVEY—PRAIRIE-GRASS FORMATION 289 
are wind-distributed, to which end the hairy awned spikelets con- 
tribute. Being perennials from heavy resistant rootstocks, they 
are well adapted to the precarious pioneer position they occupy in the 
formation. 
Two composites, taking a minor place in the formation, must be 
mentioned. While belonging to the formation proper, they function 
mainly as ruderals. Dysodia papposa, which blooms at the beginning 
of the autumnal aspect and often earlier, occurs everywhere along 
: se Fo -rest 
Fix —Autumnal aspect: an Andropogon sod, mainly A. scoparius, upon cres 
kn¢ ill; Scattered individuals of Solidago, Helianthus, and Aster are presen 
roadsides and on w astes, where it attains its greatest size and abun- 
dane 
= od 
Frequently on the most xerophytic of prairie hills and bluffs 
» assumes a very marked prominence. In our area it occurs sub- 
ently along crests and ridges, in fact anywhere that the association 
ony be Open, though it is usually depauperate in such cases. The 
fetid Marigold is an annual, and its ubiquity finds cause in the ease 
and abunc dance of its dispersal through an efficient pappus, and in 
Re period of its germination falling at the time when the majority of 
forms have long since germinated and the formation is thinning off 
it 
~~ e a hese 
farly annuals and prevernal and vernal perennials. Tot 
