1908] HARVEY—PRAIRIE-GRASS FORMATION 283 
herb from a tuberous structure, terminating in a spike bearing 
humerous heads of purplish flowers. The abundant plumose pappus 
assures a widespread distribution. 
Autumnal floral aspect 
No marked climatological change is to be noted in passing from 
the serotinal to the autumnal aspect, but simply one of gradually 
decreasing favorableness. Hence the latter has been set off partly 
for convenience of discussion, though it seems more or less distinctly 
characterized by definite floral activity; yet possibly it might be more 
accurately designated as late serotinal. Beginning in early August 
and marked by the estivation of such very conspicuous forms as 
Helianthus scaberrimus, Solidago rigida, and the bunch-grasses 
(Andropogon furcatus and A. scoparius), it extends into early October, 
When vegetative activity comes to an end. Its floral activity is 
terminated, however, in middle September by the flowering of Gentiana 
puberula and Solidago rigidiuscula, while florally the aspect is at its 
best during late August and early September, when the prairie is a sea 
of yellow from the Solidagos, mainly S. rigida, dotted here and there 
by the blue of Asters. Rising sentinel-like along higher slopes and 
crests are the rose-purple spikes of the blazing-stars, while on isolated 
knolls associations of Aster sericeus with their purplish flowers and 
White tomentose leaves relieve the sea of yellow. The bunch-grasses 
ay a very characteristic tone to the higher and more xerophytic 
nolls, 
In earlier aspects marked restriction of forms was noted, less 
“parent in the serotinal it is here scarcely evident. On the other 
and there is a marked identity of the controlling species on base, 
: lope, and crest, the entire formation presenting an unbroken and ° 
identical Covering, undoubtedly to be associated with the noticeable 
“quality of the chresard throughout these various situations. 
Eighteen of the twenty-two forms (82 per cent.) are composites, 
and all but one of these (Kuhnistera villosa) are wind-distributed. 
Like the prevernals the autumnals are pronouncedly xerophytic, 
ae into uncertain, that is unfavorable, ecological conditions, the 
Ormer at the initiation, the latter at the decline of floral activity. 
"st as prevernals have come to possess the spring period of not 
