i 9 o8] HARVEY— PRAIRIE-GRASS FORMATION 293 



canescens, more abundant but never controlling. It is distinctly 

 xerophytic, and while largely of the open association, it may work 

 down slopes into more favorable habitats. 



During the middle days of September the last two forms of the 

 prairie-grass association present their flowers, Gentiana puberula 

 blooming a few days before Solidago rigidiuscula, the last form to 

 bloom. The downy gentian occurs rarely and is largely restricted to 

 middle and lower slopes, rarely if ever occurring along the xerophytic 

 crests and ridges. Its terminal group of few large light-blue flowers 

 are rendered unimportant as the plant is of short stature (30 to 40 cm ) 

 and so hidden. It is perennial from thickened roots, and wind- 

 distributed, the seeds being widely winged. Its rarity therefore 

 lies no doubt in its high ecological requirements, being somewhat 

 mesophytic in its nature. 



The last form of the prairie to bloom is Solidago rigidiuscula. 

 Flowering as it does when S. rigida is passing into fruit, of copious 

 abundance and high frequency upon upper slopes, occurring gre- 

 gariously at times with several stalks (5 to 15) arising from the same 

 perennial root, it is rightly named the "showy" goldenrod. It per- 

 sists nearly to the middle of October, and is one of the last forms to 

 pass into fruit, though accompanying it are the later flowers of Merio- 

 lix, Ratibida, Carduus, Polygala, and Lacinaria. It is widely wind- 

 dispersed and establishment is quite general. 



Post-floral aspect 



By the second or third week in October the prairie forms of the 

 autumnal floral aspect have all passed into seed, and the gorgeous 

 yellow of Solidago rigida has given way to the somber brown of frosted 

 leaves and stalks. While seed maturation and distribution in species 

 of earlier aspects have been in progress during the subsequent aspects, 

 the post-floral aspect, extending up into late November, is particu- 

 larly characterized by this phase of plant life, yet dispersal may and 

 does continue, but in a much more limited degree even during the 

 winter season. The little fall of snow leaves the prairie bare the 

 greater part of the winter, its tone being in no way modified; the 

 post-autumnal appearance remains to characterize the prairie through- 

 out the non-flowering period, and, as has already been pointed out, 



