May, 1908.] Stream Diversion near Lakeville, Ohio. 
349 
LITERATURE. 
1. Adams, C. C. Southeastern U. S. as a center of geograph¬ 
ical distribution of flora and fauna. Biological Bull 1902; 
3:115-131. 
2. Dachnowski, A. Zur Kenntnis der Entwicklungs-Physio- 
logie von Marchantia polymorpha. Jahrb. f. wiss. Botanik 
1907, XLIV: 254-286. 
3. -, Ravines in the vicinity of Ann Arbor. 
Michigan Academy of Science, Report 9:113-122. 1905. pl22. 
4. Davenport, C. B. Statistical methods with special refer¬ 
ence to biological variation. New York. J. Wiley & Sons 
1899; and Revised edition 1904. 
5. Haacke, W. Ueber numerische Variation typischer 
Organe und korrelative Mosaikarbeit. Biol. Centralblt. 1896; 
16: 481-497; 529-547. 
6. Pearson, K. Grammar of Science. 1900. 
7. -, On the sources of apparent polymorphism 
in plants, etc. Biometrika 1902; 1:304-306. 
8. Shull, G. H. Place constants for Aster prenanthoides. 
Bot. Gaz. 1904; 38:333-375. 
9. Transeau, E. N. Climatic Centers and Centers of Plant 
distribution. Mich. Acd. of Sci. 1905; 7:73-75. 
10. Vries, H. de. Ueber die Periodicitat der partiellen 
Variationen. Ber. d. Deutsch. Bot. Gessell. 1899; 17:45-51. 
STREAM DIVERSION NEAR LAKEVILLE, OHIO* 
George D. Hubbard. 
The announcements of stream modifications have come to us 
so often in the last generation that we no longer wonder at them. 
They are very common and most of the larger streams have 
been subject to one or more of them. With all the examples 
which have been described and explained there has come a 
great variety of form and cause, yet a classification under three 
heads is possible. Some are simply diversions in which the 
stream had nothing to do but to get out of the way; these occur 
most frequently in glaciated regions. Other causes are land and 
snow slides, lava flows, volcanic eruptions and artificial obstruc¬ 
tions. Some are adjustments in which the stream modifies its 
course or the form of its valley because the one or the other is 
out of harmony or adjustment with the needs of the stream; 
these occur in regions where superposition or rejuvenation 
have occurred and the stream in its later stages is in different 
rocks from those in which it worked in youth. The third class 
^Presented to the Biological Club, February 3, 1908. 
