iqo8] HARVEY— PRAIRIE-CRASS FORMATION 287 



stock. A very limited pappus of two to four scalelike awns provides 

 only a restricted distribution, easily accounting for its gregarious 

 tendency. 



About a week or ten days later S. rigida begins its blooming, but 

 only reaches its maximum about the last of the month, at this time 

 solely characterizing the floral tone and maintaining a sea of yellow 

 for some three weeks, when the tone begins to pale as fruiting advances 

 and completely gives way during the third week of September, the 

 bright-yellow floral tone yielding to the dull-green foliage. The 

 stiff goldenrod occurs ubiquitously, but reaches its greatest abundance 

 upon middle slopes, where it is frequently copious. The single stout 

 stem (frequently several), from the perennial rootstock, rises some- 

 what over a meter, terminating in a flat dense cyme bearing numerous 

 yellow-rayed flowers, frequently 20 to 25 cm across, which with its 

 abundance and frequency makes S. rigida the most striking and 

 dominating in its floral tone of any single species of the formation. 

 Following the latter species by only a few days S. nemoralis comes 

 into bloom. Overtopped by and much less abundant than the former, 

 it never is conspicuous, though frequently it adds to the dominant 

 yellow tone of the aspect. It reaches its greatest abundance on 

 slopes, occasionally entering the open association of the crests, but is 

 rarely included in the compact sod of lower slopes. 



The three goldenrods just noted are alike perennial from a thick- 

 ened rootstock, with a tendency toward the formation of perennial 

 basal rosettes, and are widely wind-disseminated through the effi- 

 ciency of the well-developed parachute. 



Almost coincident with the blooming of these four forms is that 

 of the bunch-grasses, Andropogon f meatus and A. scoparius. Though 

 these two grasses during the last two aspects have been vegetatively 

 conspicuous upon the higher crests and most xerophytic slopes, where 

 they contribute the characteristic dull tone to the bunch-grass asso- 

 ciation, they flower only during the early part of August, thereby 

 adding but little to their already established prominence. They are 

 accompanied by Sporobolus brevifolius, which occurs less abundantly, 

 but like the beard-grasses assumes the bunch habit upon higher 

 crests and ridges. In these situations the Andropogons assume 

 facial rank, A. /meatus (fig. j) being the taller and on account of its 



