ECOLOGICAL SUCCESSION. 



345 



periods and produce smaller and larger differences in conditions, 

 due to topography, but all of these point toward a common end, 

 the peneplain. Peneplains may be local being referable to some 



c 



FIGS, i and 2. Showing a mountain in east Tennessee [Briceville Folio, U. S. 

 Geological Survey, Latitude 36 30' N. Longitude, 84 5' W. It is taken from the 

 topographic map with some of the contour lines omitted. The contour interval is 

 250 ft. (80 meters)]. In Fig. i the area (a) indicated by the dashes is at the top 

 of the mountain and represents the area covered by conifers. The blank area (b) 

 represents the area of the mountain side covered with the oak and hickory forest 

 the habitat of Cicindela sexguttata. The stippled area (c) represents the beech 

 and maple in the valley. Fig. 2. Cross section of the same. 



FIGS. 3 and 4. Showing the same mountain represented in Figs, i and 2, but 

 in an hypothetical later stage, based on the supposition that the valley at the 

 point (e) is at a peneplain level. In Fig. 3, stream (e) has cut through at the 

 point (d) of Fig. i and captured the head-waters of the stream (/). The entire 

 mountain has been sufficiently lowered to cause the conifer area to disappear ' 

 entirely. The oak-hickory area is greatly reduced and the beech-maple is greatly 

 increased, Fig. 4 is a cross section of the same (see Adams, F oi). 



