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 XXI., A) or patches of Aehus glabra. 
Some of the plants characteristic of the bare slope and open 
ridge are: 
Acerates viridifiora, Kuhnistera purpurea, 
Asclepras verticillata, Lacinaria cylindracea, 
Aster sericeus, Lactnarta scartosa, 
Bouteloua curtipendula, Lappula lappula, 
Bouteloua hirsuta, Linum sulcatum, 
Coreopsis palmata, Lobelia spicata, 
Cyperus filiculmis, Oxalis violacea, 
Cyperus houghtoni, Polygala verticillata, 
Cyperus schweinitzti, Polygonum tenue, 
Draba caroliniana, Pulsatilla hirsuttssima, 
Elymus canadensis, Ratibida columnarts, 
Flelianthus occidentalis, Lehus glabra, 
Euphorbia heterophylla, Lehus radicans, 
Fflieracitum canadense, Szlene antirrhina, 
Juniperus communes, Valertana edulis, 
Juniperus sabina, Viola pedata, 
Keleriva cristata, Viola pedatifida. 
Kuhnistera candida, 
DRY ROCK VEGETATION (Plate XXI., 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. Pel/ea 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 papyrifera, Juniperus communis, 
Campanula rotundifolia, Pellea atropurpurea, 
Camptosorus rhizophyllus, Valertana edulis, 
Cystopteris bulbifera, Zygadenus elegans. 
