282 BOTANICAL GAZETTE [ocroBER 
seems to demand only a low chresard, and upon more xerophytic 
crests than occur in our formation, where it holds its own, it appears 
copiously and not infrequently determines the tone of the open asso- 
ciation. The wind-distribution is facilitated by a copious pappus. 
Perhaps no plant of our formation has the remarkable degree of 
adaptability possessed by Lygodesmia juncea. The first plant to 
appear upon the bare exposed soil of bluffs, it persists into a well- 
formed mesophytic sod with even a marked abundance. It is to 
be reckoned as a xerophytic relict in our plot, occurring most abun- 
dantly along the crest, but at most only sparsely. It is a perennial 
from a heavy woody root, which interprets its persistence in the 
formation, and this with its reduced scalelike leaves contributes to 
its fitness as a pioneer xerophyte. The much-branched stems 
(45°™ high) end in solitary pink-rayed flowers, whose small size and 
ephemeral duration never render them florally conspicuous. Dis- 
tribution is very general and wide; the achenes are provided with 
a copious pappus. 
During the last days of the second week and early in the third 
week of July the prairie thistle, Carduus undulatus, enters upo? 
anthesis and florally characterizes this part of the aspect. Its densely 
white tomentose and much-branched stems rise some go°™ and gts 
nate in large (5°™ in diameter) solitary heads of numerous purplish 
flowers. It also assumes a gregarious habit, and patches occur here 
and there from base to crest of prairie slopes. Thus it is @ most 
conspicuous form, but reaches its maximum flowering only in early 
August. Wherever the prairie sod has been disturbed it becomes 
almost exclusive in its occupancy. It is a biennial of slightly mes 
phytic tendencies and so appeats more commonly on lower slopes: 
Its high fertility and copious pappus insure a wide distribution, easily 
explaining its very general occurrence. 
The last form to be added in the aspect is Lacinaria squarros’ 
which appears here and there upon upper slopes and crests. sh 
very xerophytic in nature, occupying a prominent place in the ea 
stages of the bluff line succession, and is in our plot to be consid 4 
as arelict. It is not conspicuous and adds little to the tone, hes 
at this time rendered bizarre by several of the earlier forms ens 
their greatest floral display. Lacinaria is an erect (50%) peren™ 
