134 TOWA ACADEMY OF SCIENCES. 



Examining' tlie results of the forej]^oiii^' measurements, 

 the chief point of interest is the ma<^nitn(h' of the "differ- 

 ences" found. These are quite large in the concentrated 

 solutions, and in the case of the double bromide of sodium 

 and cadmium diminish rather slowly with increase of dilu- 

 tion. Indeed at a dilution of 7000 litres, the difference is 

 still 33 conductivity units. The differences for the double 

 bromide of ammonium and zinc are large in the more con- 

 centrated solutions, but not so large, for equal dilution, as 

 for the double bromide of sodium and cadmium. These 

 differences decrease much more rapidly with increase in 

 dilution, entirely disappearing at dbout 1,000 litres. 



From the above results the conclusion seems justified, 

 viz.: that the two double bromides exist, to a considerable 

 extent, in the more concentrated solutions, and are com- 

 pletely broken down by water only at very great dilutions. 



In conclusion, I desire to thank Dr. H. C. Jones for valu- 

 able suggestions and aid in the ])rosecution of this work. 



THE VASCULAR CRYPTOGAMS OF IOWA AND THE 



ADJOINING PARTS OF SOUTHEASTERN 



MINNESOTA AND WESTERN 



WISCONSIN. 



BY L. H. PAMMEL AND CHARLOTTE M. KING. 



During the past year an excellent paper on Iowa Pteri- 

 dophyta, by Prof. Shimek, has appeared. 



This paper gives the distribution of the Iowa Pterido^ 

 phytes as they are represented in the Herbarium of the 

 State University of Iowa. The ferns as represented in 

 our collection somewhat extend the limits and give addi- 

 tional localities of others. It is highly desirable that 

 precise localities of our ferns be given, as it is a group of 



1 Iowa Pteridophyta in till' Hcrliariuni of tlic State University of Iowa. Bull. Lab. of 

 . Hist, of tlie State University of Iowa. 5: 14;V170. 213-21.5. VM. 



Nat 



