THE FLORA OF THE ST. PETER SANDSTONE. 22 7 



It should also be noted that Phragmidium fragarice (?) was 

 found abundantly upon Potentilla tridentata Sol., a host-plant 

 hitherto unrecorded from Iowa for this fungus. 



The flora under discussion varies more or less with the 

 texture of the rock or soil, and with exposure, and may, for 

 convenience, be considered in several groups. 



Upon the harder exposed rock surfaces the following species 

 of lichens and mosses were found: 



Lecanora rubina (Vill. ) Ach. Buellia spuria (Schaer. ) Arn. 



Physcia ccrsia (Hoffm.) Nyl. Bryum intermedium Brid. 



Parmelia conspersa (Ehrh.) Ach. Ceratodon purpureus Brid. 

 Urceolaria semposa (L,. ) Nyl. Dicranella heteromalla Sch imp. 



Placodium aurantiacum (Light. ) N. & H. 



Upon the upper portions of the ledges, in crevices, or on 

 surfaces on which a little sandy soil had accumulated, but 

 which are more or less exposed, the following species occurred: 



Cladonia cornucopioides (L,. ) Fr. Liuiim sulcatum Rid. 



Cladonia rangiferina (L,. ) Hoffm. Polygala viridescens h. 



Grimaldia barbifrons Bisch. Potentilla tridentata Sol. 



Polytrichum piliferum Schreb. Prunus pumila L. 



Sellaginella rupestris (L,. ) Spring. Aronia nigra (Willd.) Britt. 



Sisyrinchium angustifolium Mill. Scutellaria parvula Mx. 



and upon mosses, etc., in similar situations, were: 



Physcia pulverulenta (Schreb. ) Nyl. 

 Omphalia, probably umbratilis Fr. 

 Humaria — sp. ? 



Where the sandy soil on the rock ledges was somewhat 

 better developed, the following species were found: 



MuJ:Ienbergiaraccmosa(Ms..)¥>.S.Y. Hclianthemum canadense (L,. ) Mx. 



Arislida basiramea Eng. Lechca tenui folia Mx. 



Boutcloua hirsuta Lag. Polygonum camporum Meisn. 



Eragrostis frankii Steud. Gnaphalium obtusifolium L. 



Amelanchier alnifolia Nutt. Euthamia carol in iana (L. ) Greene. 



Lespedcza capitata Mx. Solidago rigid iuscu la (T. & G. ) Port. 



Amorpha canescens Pursh. Aster sericeus Vent. 



and where somewhat better shaded or protected: 



Woodsia ilvcnsis and Rubus baileyanus. 



The sandy talus below the ledges yielded the following 

 native plants: 



