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 : 



Acerates viridijlora, Kuhnistera ^iir^iit'ca, 



Asclc^ias ve7'ticillata, Lacinaria cylindracea, 



Aster scriceus, Lacinaria scariosa, 



Bouteloua curtij)cndula^ Lapfida lappula, 



Bouteloua kirsuta, Limtni sitlcatmn. 



Coreopsis -pahnata., Lobelia spicata, 



Cypertcs Jiliculniis, Oxalis violacea, 



Cypertis hotightoni, Polygala verticillaia, 



Cyperus schiveinitzii. Polygonum tenue, 



Draba caroliniana, Pulsatilla hirsutissiina, 



Elymus canadensis, Ratibida columnaris, 



Heliantlius occidentalism Rhus glabra. 



Euphorbia heterophylla, Rhus radicans, 



Hieraciuni eanadense, Silene antirrhina, 



Juniperus communis, Valeriana edttlis, 



Junipcrus sabina, Viola pedata, 



Kceleria cristata, Viola pedatijida. 



Ktihnistcra 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. Pellcea 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, Junipcrus communis, 



Cajnpanula rotundifolia, Pellcea atroptirpurea, 

 Camptosorus rhizophyllus, Valeriana edulis, 



Cystopteris bulbifera, Zygadenus elegans. 



