1908] HARVEY— PRAIRIE-GRASS FORMATION 103 



of the most conspicuous elements of the early estival aspect. Its 

 prominence, however, is of passing duration, as the petals fall after 

 several days and it passes into obscurity. Mobility is limited, result- 

 ing largely in the gregarious distribution. With Rosa, blooms Del- 

 phinium carolinianum. It is a perennial with a thick heavy root- 

 stock, and occurs sparsely as a xerophyte in the open association upon 

 upper slopes and crests. It is closely associated ecologically with 

 the bunch-grasses and invariably seems to follow them. Its single 

 erect stalk, some 6 to 8 dm high, bears a large terminal raceme of con- 

 spicuous white flowers. Rising thus so conspicuously, these plants 

 seem like sentinels of the prairie and a few individuals are noticeable 

 at some distance. Many seeds are produced, but mobility is slight. 



The anthesis of Erigeron ramosus usually precedes that of Del- 

 phinium but follows that of Rosa, only a day or two separating 

 them. Erigeron is a perennial or annual occurring along upper 

 slopes, where it assumes a copiogregarious habit of growth. It seems 

 quite restricted, few scattering individuals being noted. It is some 

 7 or 8 dm high, with several stalks rising from a single root, which 

 are terminated by spreading corymbs bearing numerous flowers with 

 yellow disks and abundant white rays; thus it is very conspicuous. 

 The achenes are provided with a double pappus, but mobility would 

 seem limited, judging from the gregarious tendency of distribution. 

 Brauneria, though occurring sparsely upon the highest slopes and 

 crests, is one of the most conspicuous early estival bloomers. It is a 

 xerophytic perennial with a large thick root. A single stalk, some 7 or 

 gdm high, is terminated by a single large head of flowers frequently 

 5 cm across. The numerous long pinkish ligulate ray-flowers surround 

 a large reddish-brown hemispheric head bristling with abundant 

 roughish chaff; in all a very prominent structure. The achenes are 

 crowned with a short-toothed pappus, thus insuring mobility, though 

 of a low degree. It is to be noted that Brauneria has a blooming 

 period of nearly two months, so it remains a conspicuous element 

 even into the following aspect. 



Scarcely have these forms flowered, when two species of secondary 

 importance begin to make their contribution to the floral aspect, 

 blooming progressively during the earlier part of the third week of 

 June. They are Anemone cylindrica and Physalis heterophylla. 



