1908] 



HARVEY— PRAIRIE-GRASS FORMA TION 



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 



Fig. 4. — Autumnal aspect: an Andropogon sod, mainly A. scoparius, upon crest 

 of knoll; scattered individuals of Solidago, Helianthus, and Aster are present. 



roadsides and on wastes, where it attains its greatest size and abun- 

 dance. Frequently on the most xerophytic of prairie hills and bluffs 

 it assumes a very marked prominence. In our area it occurs sub- 

 copiously along crests and ridges, in fact anywhere that the association 

 may 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 abundance of its dispersal through an efficient pappus, and in 

 the period of its germination falling at the time when the majority of 

 forms have long since germinated and the formation is thinning off 

 its early annuals and prevernal and vernal perennials. To these 



