TABLE OR CONTENTS. 
PAGE. 
Official Directory i 
Constitution of the Academy 3 
Members of the Academy \ 7 
Proceedings of the Fifteenth Annual Session n 
Presidents address, by W. H. Norton 17 
A Review of the Tettigonidae of North America north of Mexico, by E. D. Ball 35 
The Morphology and Function of the Amphibian Ear, by H. W. Norris — 76 
A Combination of Chromic Acid, Acetic Acid and Formaline as a Fixitive for Animal Tis- 
sues, by H. W. Norris 78 
Note on the Time of Sexual Maturity in Certain Unios, by H. M. Kelly. 81 
The Influence of Chlorine as Chlorides in the Determination of Oxygen Consumed in the 
Analysis of Water, byj. B. Weems andj. C. Brown 85 
A Study of Some Cotton Seed Oils, by J. B. Weems and H. N. Grettenberg 89 
Diphenyl Ether Derivitives, by Alfred N. Cook 94 
Some Recent Analyses of Iowa Building Stones; also of Potable Waters, by Nicholas 
Knight 104 
Contribution to the Study of Reversible Reactions, by W. N. Stull no 
Depositional Equivalent of Hiatus at Base of our Coal Measures; and the Arkansan Series, 
a New Terrane of the Carbonilerous in the Western Interior Basin, by Charles R. 
Keyes 119 
Names of Coals West of the Mississippi River, by Charles R. Keyes 128 
Volcanic Necks of Piatigorsk, Southern Russia, by Charles R. Keyes 137 
A Comparison of Media for the Quantitative Estimation of Bacteria in Milk, by C. H. 
Eckles 139 
A Method of Isolating and Counting Gas Producing Bacteria in Milk, by C. H. Eckles 144 
The Total Solar Eclipse of May 28, 1900, by David E. Hadden 145 
Preliminary List of the Flowering Plants of Adair County, by James E. Graw 152 
The Juglandaceae of Iowa, by T. J. and M. F. L. Fitzpatrick 160 
Betulaceae of Iowa, by T. J. and M. F. L. Fitzpatrick 169 
The Fagaceae of Iowa, by T. J. and M. F. L. Fitzpatrick 177 
Shrubs and Trees of Madison County, by H. A. Mueller 196 
A Terrace Formation in the Turkey River Valley in Fayette County, Iowa, by G E. Finch. 204 
Pure Food Laws, by C. O. Bates 206 
Notes on the Early Development of Astragalus Caryocarpus, by F. W. Faurot 210 
The Thistles of Iowa, with notes on a few other species, by L. H. Pammel 214 
Bacteriological Investigation of the Iowa State College Sewage, by L. R. Walker 240 
Notes on the Bacteriological Analysis of Water, by L. H. Pammel 262 
Drift Exposure in Tama County, by T. E. Savage 275 
