Article I. — The Relation of Evaporation and Soil Moisture to 

 Plant Succession in a Ravine. By Fre;d The;odore U1.1.RICH.* 



Introduction 



For some time geologists have surmised that differences in the 

 evaporative power of the air and the soil-moisture content account 

 for the succession of vegetation that accompanies the physiographic 

 changes in the development of a ravine. In order to determine 

 whether or not this surmise can be supported by experimental data, 

 this study was made during the summer of 19 13. The ravine selected 

 for investigation was the McLeish ravine, which lies in the south- 

 eastern part of the beautiful village of Glencoe, about sixteen miles 

 north of Chicago. It is mapped in the Chicago folio of the United 

 States Geologi:al Survey as a part of the Evanston-Waukegan re- 

 gion. The general geographic features of this region are the moraine 

 plain or rolling upland, the present shore, and the lake plain with its 

 associated beach ridges. The rolling upland which constitutes the 

 larger part of this area is glacial in origin, consisting of the usual 

 glacial drift, clay, sand, gravel, and boulders, and rises more than 

 sixty feet above the level of the lake. Since the ice sheet retreated, 

 some of the glacial material has been reworked by rivers, waves, and 

 winds, and thus is stratified. The heterogeneity in the composition 

 of the drift and the resulting differences in the resistance to the forces 

 of corrasion, and the great elevation of the upland above the level 

 of the lake have furnished and are furnishing excellent conditions 

 for the development of ravines. Of the many that have been carved 

 in this upland, the McLeish ravine, although one of the smaller, may 

 be considered a good representative. 



Physiography of the McLeish Ravine 

 (Plate xvni) 



It would be foreign to this study to give a complete exposition of 

 the geology and physiography of the ravines of this upland region. 

 Such a presentation is given by Atwood and Goldthwait ('08). How- 

 ever, an intelligent appreciation of the method and results of this 

 study requires a brief description of the location and direction of the 



*Accepterl by the University of Chicago for the degree of Master of Arts in 

 Botany. 



