230 ILLINOIS ACADEMY OF SCIENCE 



abundantly on the north- and east-facing slopes, but they 

 were also found near the base of the south-facing slopes. 

 Vines were quite numerous and luxuriant near the base of 

 the slopes ; particularly in the vicinity of the lake, in the 

 larger ravines. Vitis (sp.) and CeJastriis scandens were 

 the ones most commonly found. 



An observation was made in the McLeish, N. T. 8, dur- 

 ing January on the moisture content of the soil of east 

 and west-facing slopes of the ravine. The soil on the west- 

 facing slope of the ravine on which the sun was shining 

 seemed relatively dry, while the water was seeping out of 

 soil on the east-facing slope of the ravine. The connection 

 between this and the plants found on the two slopes was of 

 equal interest. There was almost no herbaceous growth 

 on the west-facing slope, while the east-facing slope was 

 thickly covered with moss. 



The slanting and overturned trees in the older ravines, 

 as show n in Fig. IS, demonstrated the fact that there is 

 slow erosion and slumping taking place on the ravine 

 slopes. This slumping of the land is probably due to the 

 abundance of seepage water in clay soil. 



Small unweathered pieces of rock (Niagara limestone) 

 were found on the slopes along the entire length of 

 Ravine 3. 



This study of the ravines has demonstrated how factors 

 of varying intensity, at the eroding areas of ravines — the 

 mouth and head — in the form of wind, waves, light, alter- 

 nating temperatures, stream erosion, and soil movement 

 due to seepage water, have affected vegetation. 



In the intermediate areas of ravines, where erosive fac- 

 tors are practically nil in their effects, it is of interest to 

 note, how the slight modification of light and moisture 

 conditions, brought about by the change in aspect of slope, 

 cause an immediate difference in the composition of the 

 herbaceous vegetation on the opposing slopes. 



Summary and Conclusion. 



The plant successions of Glencoe are primarily deter- 

 mined by topography, and are distinguished from one 

 another by the presence, absence or combination of certain 

 physical factors. The important factors in determining 



