April, 1906.] Observations— Flora of the Shale Bluffs. 



501 



light humus going first, carrying with it the herbaceous plants, 

 followed by the shrubs, leaving the larger trees with their securer 

 holdfasts until last. The erosion may cease at this point, or it 

 may go on until the slope becomes precipitous and is swept of 

 its last vestige of vegetation. 

 In either case, the plants 

 mentioned as being in the 

 xerophytic zone above, may 

 begin to creep down as soon 

 as sufficient earth has been 

 washed down to enable them 

 to thrive. 



Owing to the great isola- 

 tion of the different ravines, 

 there is less uniformity in the 

 succession of the different 

 plant societies than might 

 otherwise be expected. Es- 

 pecially is this true of the 

 earlier stages. Some of the 

 first plants to appear on the 

 pure exposed shale are the 

 annuals Anychia dichotonia, 

 A. Canadensis and Oxalis 

 stricta. In some places nearer 

 to civilization, Melilotus alba 

 is one of the earliest occupants of the naked cliffs. In the 

 shrubby thicket which follows, there is usually a great dearth 

 in the number of species. Rubus nigrobaccus may be un- 

 iformly relied upon to appear first, while V accinium vacillans, 

 Gaylussacia resinosa, Anielanchier Canadensis and Acer rubum 

 are always found in the dryest, hottest and most exposed shales; 

 and these, with a carpeting of lichens, mosses and Danthonia, 

 may immediatel}^ be followed by a young sturdy growth of white 

 and red oaks. 



In ravines where the shale is kept moist by springs, or on 

 the dry, southern and western exposures. Solidago caesia, S, 

 flexicaulis, Aster macrophyllus, Rubus occidentalis , as well as R. 

 nigrobaccus, Hamamelis Virginiana, with ferns, mesophytic 

 mosses and liverworts obtain a foothold here, perhaps earlier 

 than usual and are quite abundant. 



An interesting plant society was found on a bluff at High 

 Banks on the Olentangy River. This magnificent bluff is over 

 one hundred feet in height, exposed to the rays of the afternoon 

 sun, and in places so steep and the rock so loose that no vegeta- 

 tion has been able to gain a foothold. But few trees are found 

 on this exposure; straggling and shrubby red and white oaks, 



Fig. ] . View in upper end of a narrow ravine 

 showing character of the vegetation. 



