68 SEVENTH REPORT. 



: A STUDY OF PLANTS IN RAVINES NEAR ADRIAN. 



FRANCES L. STEARNS. 



An attempt has been made to correlate the development of vegetation 

 of the river valley with the i^hysiographic changes which have marked the 

 history of its establishment. These, briefly outlined, are the gully, the 

 ravine, first with steep sides and later with a gentler slope, the bluff, and 

 flood plain with meandering streams — this study does not include the 

 flood plain. 



The area worked on is a small part of the bank of the Raisin River at 

 Adrian and the ravines of one of its tributaries. The Raisin is a small, 

 sluggish stream meandering in a valley one-half to one mile wide with 

 outer banks 25 to 100 feet high and at this point drains a part of the De- 

 fiance terminal moraine. The moraine forms knolls and depressions and 

 the small streams are continually cutting back gullies and ravines. The 

 soils are various, gravelly till, clay, sand and muck, seeming to be scat- 

 tered without any system. Part of the drift is land-laid and in other 

 places the gravel and sand is sorted by water and distinctly stratified. 

 The development of the drainage is closely allied with the glacial history 

 of the region and the mature river valley in its present condition may have 

 passed through stages not now illustrated by any portion of the system, 

 but various phases appear which can be taken as stages in the develop- 

 mental history. 



The initial stages of ravine formation are seen in the gullies. Where 

 the original forest covering has been cut and the land is under cultiva- 

 tion the gulh^ eats back rapidly, the washouts being most destructive in 

 sandy and gravelly fields, no Avater remaining in the gull3\ 



The first gully studied was in a cultivated field and was in a broad 

 depression. It was about 50 feet long and 6 feet deep and cut through 

 sand underlaid by clay. The shifting of the newly exposed soil pro- 

 duces nearly desert conditions. The plants which do develop are annuals 

 or plants which have fallen down the side carried by part of the bank or 

 those which spread by rootstalks. 



The weeds of the cultivated field early gain a foothold on more stable 

 sides. These are such plants as ragweed. Ambrosia artemisia^folia, 

 Lactuca scariola, Plantago major which are characterized by rapid growth 

 and seed dispersal and protection from destruction by animals. Other 

 weeds from neglected meadows, such as Aster and Thistle, are introduced 

 by the seeds carried by wind. The most striking example of plants 

 spreading by root stalks is Rumex acetosella. This is best seen in the 

 second gully studied. This was in the same field and was about 90 feet 

 long, 20 feet deep and cut in sand. Here Rumex sends, rootstalks often 

 five feet long down the side of the bank, acting as a soil binder.) The 

 same work is done less perfectly by grasses and sedges. This gully is very 

 barren of vegetation, fewer weeds having developed than in the first. In 

 the first of these gullies a small part of the side was covered by a char- 

 acteristic ravine growth. Where the water seeped out of the soil, keep- 



