392 E. LUCY BRAUN 



Plants confined to conglomerate rock areas. A few of the plants 

 of the conglomerate rocks are confined to this habitat within the 

 Cincinnati region; others are usually confined to the sandy or 

 gravelly soil of terraces; and still others are of rather general 

 distribution. The most characteristic plants of the various 

 stages are the plants of most limited distribution. Dermato- 

 carpon minidtum is known from only one rock area with out- 

 crops at short intervals over a distance of about a mile. Walk- 

 ing fern {Camptosorus rhizophyllus) and Cystopteris bulbifera 

 are confined to conglomerate rocks within this region. These are 

 characteristic plants of limestone cliffs throughout a wide geo- 

 graphical range, and have been recorded from stations 50 to 100 

 miles from here, but are not known to occur in the intervening 

 area. Many of the secondary species, and a few of those deter- 

 mining the facies, are of less limited distribution, but by no means 

 general in the region. Thus Mitella diphylla, Woodsia obtusa, 

 Aquilegia canadensis, Arabis Drummundi, Physocarpus opuli- 

 f alius, and Silene virginica (usually) are confined to the relatively 

 small areas of sandy or gravelly soil ^\dthin the Cincinnati region. 



The vegetation of the conglomerate rocks of the Cincinnati 

 region represents an isolated plant community deriving some of 

 its members from the ordinary vegetation of the region; others 

 from the vegetation of the nearest related soil areas of the 

 region; and still others — the most characteristic elements in 

 this rock succession — are not represented elsewhere in the re- 

 gion, and must have been derived from distant similar habitats. 



