Wheeler : FLORA OF SOUTHEASTERN MINNESOTA. 367 



BARE SLOPE AND OPEN RIDGE VEGETATION. 



The soil of the southern slope and open ridge is generally 

 largely formed of sand and broken limestone. It becomes very 

 dry early in the summer, and then appears almost bare of 

 vegetation except where it is broken by scattered junipers 

 (Plate XXL, A) or patches of Rhus glabra. 



Some of the plants characteristic of the bare slope and open 

 ridge are : 



Aceratcs viridiflora, Kuhnistera purpurea, 



Asclepias vcrticillata, Lacinaria cylindracea, 



Aster sericeus, Lacinaria scarwsa, 



Boutcloua curtipcndula, Lappula lappula, 



Boutcloua hirsuta, Linum sulcatum, 



Coreopsis palmata, Lobelia spicata, 



Cyperus filiciilmis, Oxalis violacea, 



Cyperus houghtoni, Polygala verticillata, 



Cyperus schiveinitzii, Polygonum tenuc, 



Draba caroliniana, Piilsatilla hirsutissima, 



Elymus canadcnsis, Ratibida columnaris, 



Hclianthus occidentalism Rhus glabra, 



Euphorbia heterophylla, Rhus radicans, 



Hicracium canadense, Silene antirrhina, 

 Juniperus commum's, Valeriana cdulis, 



Juniperus sabina, Viola pedata, 



Kcelcria cristata, Viola pedatifida. 



Kuhnistera Candida, 



DRY ROCK VEGETATION (Plate XXL, B). 



The rock plants and sand plants do not in many places form 

 distinct groups. The sand of the bluffs nearly always contains 

 considerable broken limestone and thus furnishes conditions 

 favorable to the growth of limestone plants. Pellcza atropur- 

 purea and Camptosorus rhizophyllus seem to be the only ones 

 that are restricted to the bare limestone. The former prefers 

 dryer and more exposed locations than the latter. 



The characteristic plants of dry rocks are : 



Betula papyri/era, Juniperus communis, 



Campanula rotundifolia^ Pellaa atropurpurea, 

 Camptosorus rhizophyllus^ Valeriana edulis, 



Cystopteris bulbifera, Zygadenus elegans. 



