ON CLAY 



211 



on the north side of the jetty. Materials thus deposited gradually 

 pile up to such an extent as to protect the base of the cliff from 

 wave-action. Thus the effect of the slumping of the springtime 

 (which tends to reduce the angle of slope) is not fully removed from 

 year to year. 



d 



Fig. 158. — The bluff habitats near Glencoe, 111., showing several stages in the 

 development of the forest on the bluff. The area to the right of a line between a and b 

 is stable enough to support some sweet clover. Here the tiger-beetle larvae, spider, 

 etc., are most abundant. The area between lines joining a and b and a and c is in the 

 early shrub stage. To the left of ac the shrubs are denser and larger, and some trees 

 are present. Reprinted from the Journal of Morphology. 



2. SWEET-CLOVER ASSOCIATION 



(Fig. 158) (55) 

 Under the condition described above, the water of rainfall, as well 

 as the slumping, reduces the angle of slope, and the bluff becomes more 

 and more stable. Some of the clods of turf from the top of the bank 

 stop half way down the slope. The bluff begins to support a few xero- 

 phytic plants, such as the sweet clover, asters, etc. 



