[derick] two plant ASSOCIATIONS 69 



one may regard the "natural vegetation as an indicator of the cap- 

 abiHties of land for crop production," but "the entire plant cover is a 

 better indicator than the presence or condition of a single species." 



Though the following lists may be imperfect, they suggest that 

 a district, whose flora so closely resembles that of fertile areas 

 further south, described by Shantz, might be profitably brought 

 under cultivation. 



(A) Plants From the Higher Sandy Areas 



1. Cladonia pyxidata, (L) Fr. (Lichenes). A fragmentary 

 specimen of a lichen which apparently occurs abundantly upon the 

 depressed areas. It is described in connection with the latter. 



2. Polytrichum piliferum, Schreber (Musci). A moss well 

 represented in the depressions. Only one specimen was noted in the 

 collection from the higher areas. 



3. Selaginella rupestris, (L). Spring. (Lycopodiales) . A form 

 quite common, especially in the west, on sand, barren hills and rocks. 

 Macoun reports it as ranging from Ottawa, on sand hills throughout 

 the prairie region, to British Columbia. 



It is a small Selaginella, growing in close tufts from 2 to 6 cm. 

 high, with closely appressed leaves each tipped with a bristle. The 

 sessile spikes are quadrangular, the sporophylls being somewhat 

 broader than the foliage leaves. 



4. Bouteloua gracilis (H.B.K.) Lag. (Bouteloua oligoslachya, 

 (Nutt.) Torr.) (Gramineae). The Blue Grama, a grass characteristic 

 of the prairies and found from Mexico to Manitoba. It is a shallow- 

 rooted, tufted plant, which withstands fire well. The culms are 

 slender and erect, 1-5-5 dm. high. The sheaths and leaf blades are 

 smooth. At maturity the latter are convolute. The spikelets are 

 sessile and crowded in two rows along one side of a flattened rachis. 

 The fertile lemma is three-cleft with awned divisions, the sterile is 

 two-lobed with two divergent awns and a tuft of hairs at the base. 

 It blossoms from July to September. 



5. Muhlenbergia gracillima, Torr. (Gramineae). This Ring 

 Grass is a perennial found on the prairies and throughout the western 

 United States. Shantz reports it as characteristically associated with 

 Bouteloua. It may be recognized by its loose, long panicles; by the 

 unequal, empty glumes, the second of which is awned, and by its long 

 lemma with an awn 2-4 mm. long. It blooms in the late summer or 

 autumn. 



6. Pulsatilla ludoviciana, (Nutt). Heller (Ranunculaceae). 

 The Pasque-flower, Blue Tulip, Wild Crocus, Lion's Beard or Prairie 



