362 Prairie Flora 



are so hard to cut with a breaking plow, blooms a little later. Its 

 flowers are not nearly so showy, while its densely canescent foliage 

 serves largely to give the prairies their prevailing gray tint. Two 

 species of Lepidium are in bloom by road sides and on waste ground. 

 By the middle of June, the red flowers of Phlox pilosa are to De seen 

 everywhere, while the marsh vetchling, Lathyrus palustris, is blooming 

 in low rich places. The vetches are especially common about gopher 

 mounds. Towards the close of June, the silvery-white foliage of 

 Psoralia argophylla begins to be dotted with its deep purple flowers. 

 Among the rarer June flowers is Agoseris glauca, a plant of western 

 range, observed in Big Stone county. 



Early in July the grayness of the prairie due to the Amorphas and 

 Psoraleas is heightened by the whitening glumes of the ripening poreu- 

 pine grass, 8tipa sparatea. The loosening seed grains with their long 

 spiral awns work through one's clothing and irritate one's flesh in a 

 way never to be forgotten. The Canada milk vetch. Astragalus canot 

 densis, becomes a conspicuous object on the prairie where the soil has 

 been loosened by the pocket gopher. Where the soil is somewhat moist 

 the whitely tomentose showy milk weed, Asclepias speciosa, raises its 

 stout stem thickly covered with its large oval leaves, carrying at its 

 top its clustered umbels of large flowers. In dry places the rough 

 ox-eye, Heliopsis scahra, begins to bloom, — a forerunner of the great 

 show of Compositae to follow. In rich places the showy tick-trefoil, 

 Be^modium canadense, may be seen in bloom, together with two 

 prairie clovers, Petalostemon purpureum, the latter being one of our 

 most showy prairie flowers. The tall Elymus canadensis with its nod- 

 ding head is now one of the most notable of prairie grasses and the 

 fleld thistle, Cir^ium discolor, is becoming a conspicuous object every- 

 where. Its flowers are light purple or pink, while its stems and the 

 under sides of its leaves are densely white tomentose. Occasionally 

 one flnds a white-flowered plant. Scutellaria parvula is a modest and 

 unassuming plant on level ground, while Chenopodium alhum grows up 

 in waste places. 



In the early part of August the tall stems and purple spikes of 

 the big blue stem grass, Andropogon furcatU6, are conspicuous objects 

 on rich moist prairies. Indeed, one who has seen this noble grass in 

 great areas growing on the wild prairie, especially if he has seen it in 

 full bloom in early morning swaying before a gentle south wind, will 

 have impressed on his mind a sight never to be forgotten. This grass 

 was the blue stem of the early settlers, and the hay made from it was 

 more prized than that of any other grass. In these rich upland 

 meadows there is sometimes found the tall meadow rue, Thalictrum 

 purpurascens, always a conspicuous object. On rich soil the great 

 rag weed. Ambrosia triflda, grew to immense proportions, often form- 

 ing thickets where horses and rider might be concealed from view; 

 while the common rag weed. Ambrosia artemisiae folia was found on the 

 prairie everywhere. Both of these rag weeds became pernicious 

 weeds, after the cultivation of the prairies began, and grew much 

 larger on cultivated ground. The rough cinque foil, Potentilla mons- 

 peliensis, is occasionally found on the prairies, but is not so common 

 as in the older parts of our country. Convolvulus sempium grows 



