282 BOTANICAL GAZETTE [october 



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 cm 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 upon 

 anthesis and florally characterizes this part of the aspect. Its densely 

 white tomentose and much-branched stems rise some 90 cm and termi- 

 nate in large (5 cm 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 a 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 meso- 

 phytic tendencies and so appears 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 squarrosa, 

 which appears here and there upon upper slopes and crests. It is 

 very xerophytic in nature, occupying a prominent place in the early 

 stages of the bluff line succession, and is in our plot to be considered 

 as a relict. It is not conspicuous and adds little to the tone, which is 

 at this time rendered bizarre by several of the earlier forms now in 

 their greatest floral display. Lacinaria is an erect (5o cm ) perennial 



