TABLE OF CONTENTS. 
Page. 
Letter of Transmittal. Ill 
Table of Contents V 
Oflacers of the Academy VI 
Membership of the Academy T, VII 
Proceeding's of the Twentieth Annual Session l 
Presidential Address, by Melvin F. Arey 7 
Photographic Accessories of the Drake Observatory, by D. W. Morehouse 
-Plates I-III 15 
Municipal Hygiene— Part II— Milk, by C O. Bates 17 
An Observation on the Number of Bacteria in Des Moines School Build- 
ings, by L. S. Ross 21 
A Flora of Webster County, Iowa, by O. M Oleson and M. P. Somes 25 
Floristic Notes from on Illinois Esker, by Bruce Fink —Plates IV-VI 59 
Lichens and Recent Conceptions of Species, by Bruce Fink 65 
Notes on the Discomycete Flora of Iowa, by Fred Jay Seaver 71 
The Forest Trees of Eastern Nebraska, by Charles E. Bessey 75 
Some Diseas es of Rocky Mountain Plants , by L. H. Pammel— PlatesVII-XII 89 
The Liliales of Iowa, by T. J. Fitzpatrick 115 
Some of the Flowering Plants of Calcasieu Parish, Louisiana, by J. M. Lind- 
ly-Plate XIII 161 
Dolomite and Magnesite with Reference to the Separation of Calcium and 
Magnesium, by Nicholas Knight and Ward H. Wheeler 167 
Logarithmic Factors for Use in Water Analysis, by W. S. Hendrixson 173 
Periodical Literature in Iowa on the Subject of Chemistry, by W. S. Hen- 
drixson 175 
Action of Bromic Acid on Metals, by W. S. Hendrixson 179 
Some Variant Conclusions in Iowa Geology, by J. E. Todd 183 
More Light on the Origin of the Missouri River Loess, by J. E Todd 187 
Geology of the Corinth Canal Zone (abstract), by Charles R. Keyes— Plates 
XIV-XV 195 
^ Lime Creek Fauna of Iowa in Southwestern United States and Northern 
Mexican Region, by Charles R Keyes 197 
. -Alternation of Fossil Faunas, by Charles R. Keyes.... 199 
A Contribution to Madison County Geology, by F. A Brown 203 
An Attempt to Illustrate Tides and Tidal Action, by John L. Tilton— Plate 
XVI 207 
The Holding and Reclamation of Sand Dunes and Sand Wastes by Tree 
Planting, by H. P. Baker 209 
A Study of a Portion of the Iowan Drift Border in Fayette County, Iowa, 
by Grant E. Finch 215 
Mutual Induction and the Internal Resistance of a Voltaic Cell, by L. 
Begeman 219 
Cyclonic Distribution of Precipitation, by J. A. Udden— Plate XVII 223 
The Physical Laboratory at Iowa College, by F. F. Almy 227 
A Simple Demonstration of the Doppler Effect in Sound, by F. F. Almy 229 
The Effect of Pressure upon Lines in the Spectrum of Iron, by F. F. Almy. 231 
Electrical Standards, by Karl E. Guthe 233 
' Studies of the Collembolan Eye, by J. E. Guthrie— Plate XVIII 239 
- A Study of the Choroid Plexus (abstract), by Walter J. Meek 245 
, The Carotid Arteries and their Relation to the Circle of Willis in the Cat, 
byH.W. Norris 251 
The Desparity between Age and the Development of the Human Family, 
Illustrated by Pronounced Cases due to Thyroid Iilalformations, by 
James Frederick Clarke— Plates XIX-XXVII 257 
Relation of the Motor Nerve Endings to Voluntary Muscle in the Frog, by 
B. A. Place-Plate XXVIII 261 
Oladocera of Des Moines and Vicinity, by B. O. Gammon 267 
-Food of Subterranean Crustacea, by L. S. Ross 273 
