MICHIGAN ACADEMY OF SCIENCE. 113 



CONTRIBUTION TO THE BOTANICAL SURVEY OF THE HURON 



RIVER VALLEY. 



Alfred Dachxowski. 



ravines in the vicinity op ann arbor. 



The following here presented is the outcome of study in the field carried 

 on during the summer and autumn of 1904, and supplemented b}^ further 

 work of a more recent date at the suggestion of Dr. George P. Burns, to whom 

 the writer desires to express his indebtedness for much helpful advice. As 

 a preliminary note for an investigation of the casual relation existing be- 

 tween habitat and plants in this vicinity, the present paper includes the 

 ravines situated along the bluff near the river east of Ann Arbor, in the 

 wooded section known as School-girl glen, and the ravines in Cascade glen 

 and near Foster, distances three and five miles (18 km. and 30 km.), respec- 

 tively v.est of Ann Arbor. The objects of this study were to trace out the 

 chief plant associations, and to correlate their distribution with the var- 

 ious ecological factors active in this region. Primarily these data are to be 

 introductory to a more detailed and extended study, under measured con- 

 ditions, of the varying activity of plants, as individuals and as associations, 

 i. e., the attempt is made at field work in experimental physiology. In ad- 

 dition, though these floristic notes do not complete the needed investigations, 

 it is expected that some light may be thrown on the probable succession 

 of local vegetation. Hence, as a record for comparison of future changes, 

 or an endeavor to indicate in a general way some of the conditions involved, 

 a local study of this kind seemed desirable. 



The soil of the Huron river valley is throughout of glacial origin. In 

 this vicinity the numerous rounded morainal hills and similar depressions, 

 the characteristic features of a drift area, betray the youthful topography; 

 and an interesting display of dynamic phenomena is everywhere apparent. 

 The river is bordered by banks SO to 250 feet (24 m. to 76 m.) high, but sel- 

 dom reaching more than 300 feet (90 m.). The slopes are more or less gradual. 

 Details of general geography, the geology and topog'raphy of this region 

 have been so well treated by several writers, that to avoid reiteration, ref- 

 erence is made to the work of Leverett (1), and the papers of Reed (2), Weld 

 (3), and Brown (4). 



Variations in climate are not very considerable. Here also referring, 

 for a more detailed account, to a recent paper (5), the following are the 

 chief climatic features for Ann Arbor (*) : The winters, marked by a dimi- 

 nution of precipitation, are relatively mild as compared with other coun- 

 tries. Usually the freshets during March and April are less decided than 

 during July and August, at which time the highest water occurs after the 

 heavy rains; the temperature is at the highest also. This year (1905), 



1 Leverett, F. The glacial formations and drainage features of the Erie and Ohio 

 basins, Mon. 41, U. S. G. S. 



2 Reed, Howard S. The Ecology of a glacial lake, Bot. Gaz., 34: 125-139, 1902. 



3 Weld, Louis H. A peat bog and morainal lake, Bot. Gaz. 37: 36-52, 1904. 



4 Brown, Forest, B. H. The Plant societies of the bayou at Ypsilanti, Michigan, 

 Bot. Gaz. 40: 264-284, 1905. 



5 Transeau, E. N. 



* Comparative data taken from the Annual Summary of the Michigan section of the 

 U, S. Weather Bureau Climate and Crop service. 



