1908] HTARVEY—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°) 
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- 
“sts 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- 
lx, Ratibida, Carduus, Polygala, and Lacinaria. It is widely wind- 
‘persed and establishment is quite general. 
Post-floral aspect 
By the second or third week in October the prairie forms of the 
‘utumnal 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, 
i Post-floral aspect, extending up into late November, is particu- 
rly characterized by this phase of plant life, yet dispersal may and 
does Continue, but in a much more limited degree even during the 
“inter season. The little fall of snow leaves the prairie bare the 
Seater part of the winter, its tone being in no way modified; the 
oer etumnal appearance remains to characterize the prairie through- 
non-flowering period, and, as has already been pointed out, 
