PREFACE 



Weeds do an enormous damage to 'the crops of Iowa. A con- 

 servative estimate places the injury at $25,000,000 annually. This 

 loss could be largely avoided if we had more concise information 

 on the subject, land if we could conserve the matchless resources 

 of our soil by keeping the weeds down, the farmers would be greatly 

 benefited in a financial way.' It would seem appropriate, therefore, 

 to publish a volume of the Weed Flora of the state at this time. 



The need of a volume dealing with Iowa weeds as a feature of 

 the flora of the state has long been felt by the public schools. 

 Many papers have been published by the Iowa Agricultural Ex- 

 periment Station, but these papers are mostly out of print. This 

 work is much more comprehensive than anything heretofore pub- 

 lished in this state. The title indicates that it is not a weed book, 

 but rather a weed flora. Much stress has been laid on the geograph- 

 ical distribution of weeds. It is a contribution to the local flora 

 of the United States. 



The chapter on the geographical distribution of weeds will be 

 found of special interest to the phytogeographer. I desire to ex- 

 press my thanks to Dr. M. L. Fernald, Messrs. R. I. Cratty, F. W. 

 Paige, 0. M. Olson, J. P. Anderson and Prof. B. Shimek for assist- 

 ance in giving the geographical distribution of Iowa weeds. The 

 chapter on the microscopic structure of weed seeds brings together 

 in English much on the subject which has hitherto been inacces- 

 sible to the student not familiar with German or French litera- 

 ture. The chapter on morphology will greatly help the student to 

 understand the changes occurring in the development of the flower 

 and the formation of the &eed. The chapter on the use of weeds 

 in medicine will be of interest to those who occasionally make use 

 of wild plants for medicinal porposes. The chapter on seeds de- 

 scribes la large number of weed seeds ; this will be found of value 

 to thos'e engaged in a study of seeds. 



The chapter on various weed laws gives a summary of laws 

 in various states in the Mississippi Valley. In compiling these 



