MICHIGAN ACADEMY OP SCIENCE. 69 



ing the surface moist, mosses, alg?e and liverworts appear. Oscillatoria, 

 Botrychium and Conocephalus occur together. 



The third gully is in open pastured oak-hickory v/oods. The soil is 

 sand with a clay layer below. In this gully or 3'oung ravine there is great 

 conservation of moisture and we find a smaller development of weeds; 

 shrubs, blackberry and raspberry, gain a foothold; there is a greater 

 development of hydrophytic mosses and algae; the more hydrophytic 

 plants characteristic of river margin invade the ravine running back from 

 the river, examples are Prunella vulgaris and Impatiens biflora; herbs 

 of oak-hickory forest, as Campanula rotundifolia, occasionally occur. 



Gullies cut in the deeply shaded forest where there has been little 

 change of drainage progi'ess more slowly, since they are filled by ac- 

 cumulation of vegetable matter which enriches soil, holds moisture and 

 prevents destruction by rain wash. The desert condition rarely appears 

 in these localities or is of short duration. The gtuHies on the river bank 

 studied are of this type, but are not in natural condition, being held 

 by brush, etc. 



A desert condition may also occur when the meandering stream cuts 

 into the old outer bank. Here banks 20-50 feet of clay or sand rise almost 

 vertically from the river and are devoid of vegetation except that which 

 falls from the top. In this locality the destruction seems more rapid in 

 clay than in sand, just the opposite being true for lateral extension of 

 gullies. 



Ravine I is three hundred feet long and thirty or more feet deep at 

 its oldest part widening to twenty-five feet. It is cut partly in clay and 

 partly in sand. There is an oak-hickory forest on the west and culti- 

 vated field on the east. Near the head the banks are washed out, 

 forming side gullies, farther down Ave have true ravine, well developed, 

 passing into a broad ravine at the outlet. The gullies are sand and are 

 desert or are held by blackberry thickets in whose shade mesophytic 

 herbs develop. There are also climbers, Rhus and Ampelopsis. 



As some stability of bank is attained two groups of plants appear, a 

 group of shrubs abutting on the forest and represented by Carpinus Car- 

 oliniana and Hamamelis Virginiana and a rich flora of mesophytic herbs 

 on shady banks ; this includes Adiantum pedatum, Trillium grandeflorum, 

 Thalictrum dioicum, Mitella diphylla. The shrub zone rarely reaches the 

 water's edge, but the stream is bordered by herbs and more hydrophytic 

 plants, as Conocephalus, which also grow on the wet clay bank. These 

 plants are adapted to shade, they bloom early and have thin leaves. 



Scattered groups of Acer rubrum and Populus tremuloides occur on 

 the bank. 



In the shade of these shrubs and trees seedlings of the oak-hickory 

 forest are developing and young Ulmus Americana, Tilia Americana, and 

 Fraxinus Americana are found. 



In Ravine II practically the same relation of plants is found, but heavy 

 blue clav is in all of the bottom and there is a much larger area covered 

 by hydrophytic plants and stream margin and bog plants are found. 



A broad ravine is found on the bank behind the cemetery where a small 

 stream cuts through the river bank. Here we have deep shade and the 

 size of the trees shows great age. There is an absence of pioneer plants 

 even on the cut sides. The gully is filled by leaves. The characteristic 

 thing is the mesophytic trees, Tilla Americana, Ulmus Americana, Acer 



