FORESTRY SURVEY 227 



The forest to the south was quite different in aspect 

 from the one to the north. It might more properly be 

 called a transition forest. The vegetation at the base of 

 the slope consisted of species found in the Populus-shrub 

 and the Juniperus-shrub associations. At the center of 

 the bluff these forms overlapped the upland species of 

 trees and shrubs. The trees here were small, and the 

 vegetation was dense. The plant population was compara- 

 ble to that of any upland forest. 



3. The Eavine. 



All of the ravines in tliis region are drained by Lake 

 Michigan. There were no ravines in the initial stages of 

 topographical development in this territory. Of the seven 

 ravines studied only two were in the earlier stages of 

 development. Considered floristically. and taking the 

 entire ravine into account, there is no such thing as an old 

 ravine, for every ravine has its characteristic flora at the 

 mouth, where vegetation may or may not be present, the 

 head, and in the intermediate area. The vegetation found 

 at these places recapitulates the life history of the vegeta- 

 tive cycle of the developing ravine from its earliest stages. 



a. Mouth. — The mouths of ravines varied in both topo- 

 graphic and floristic aspect. The mouths of the RaN'ines 

 1, 2. 3 and 4 were, on the whole, less affected by erosion 

 than Eavines 5, 6 and 7. This may have been partly due 

 to the fact that the beaches were wider in X. T, 6 at these 

 points, and hence the slope was protected from the de- 

 structive effect of the waves. The mouth of Eavine 5 in 

 X. T. 8. 8 is that of a ravine practically in its initial stage. 

 It had an extremely xerophytic aspect. Fig. 15 gives its 

 aspect as studied by Dr. Cowles eighteen years ago when 

 the entire ravine was in the initial stage of its develop- 

 ment ; Fig. 16 gives the present aspect of the same ravine. 

 Lateral erosion has caused the widening of the ravine, and 

 although still xerophytic in aspect, the planting of black 

 locust has succeeded in partially stabilizing its face. The 

 mouth of Eavine 2 was almost entirely devoid of vegeta- 

 tion. The north-facing slope of this ravine, however, was 

 covered with vegetation. 



