PREFACE

Weeds do an enormous damage to the crops of Iowa. A conservative estimate places the injury at $25,000,000 annually. This loss could be largely avoided if we had more concise information on the subject, and 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 Experiment Station, but these papers are mostly out of print. This work is much more comprehensive than anything heretofore published 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 geographical 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 express my thanks to Dr. M. L. Fernald, Messrs. R. I. Cratty, F. W. Paige, O. M. Olson, J. P. Anderson and Prof. B. Shimek for assistance 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 inaccessible to the student not familiar with German or French literature. 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 seed. 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 describes a large number of weed seeds; this will be found of value to those 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

laws I have been aided by Mr. Small of the Iowa State Library, Mr. Moore of Wisconsin, Mr. Michel of South Dakota, Dr. Howard of Missouri and H. L. Bolley of North Dakota.

In the preparation of this Weed Flora, I have been greatly assisted by Professor J. N. Martin, who has written the chapter on morphology of the plant; Miss da Hayden, who has written the chapter on dissemination; Professor J. C. Cunningham, who has written the chapter on roots and underground organs; Miss Charlotte M. King, who is the joint author of the chapters on gross characters and microscopic structure of seeds. Miss King is also responsible for many of the excellent drawings. The chapter on medicinal weeds was prepared by Miss Kellogg. I am greatly indebted to her for painstaking editorial work and for preparing the bibliography and the index. In the matter of bibliography, it has seemed best to divide the subject into various sections so that the student may easily find the desired literature. The bibliography is not complete but enough papers are given to enable the student to find the important literature. I am indebted to Dr. Clark, of the Canadian Seed Laboratory, for the privilege of using some of the admirable illustrations of the Canadian work on weeds, also to Dr. Ernest Bessey for illustrations from Beal's Weeds of Michigan, and the classical Hillman seed figures in the Michigan bulletin, and to the Nevada Station for the use of the Hillman cuts. Some of the Hillman and a few other figures have been taken from the government publications. I am also indebted to various publishers for figures which have been taken from several textbooks of botany, as the Bergen & Davis book published by Ginn & Co.; several botanical works like Thomé's published in German, and to the Connecticut Experiment Station. A few figures have been taken from the Botanical Gazette. Credit is given under each figure. The photographs were made by F. E. Colburn, photographer at the Iowa Agricultural Experiment Station, G. T. Hart and C. R. Quade. The clerical work of the volume was performed by Miss Bertha Herr and my daughter, Miss Harriet. Mr. Burlingmair assisted in a study of weeds in different fields. To Mr. James H. Lees for his assistance in proof reading and editorial work I am also indebted. To all I wish to express my sincere thanks.

The reader will find it advisable to have several of the recent treatises on weeds. Mention may be made of my work "Weeds of the Farm and Garden," a general treatise of three hundred pages

with numerous illustrations; the work of Fletcher and Clark of Canada; Bolley's "North Dakota Weeds;" Blatchley's "Indiana Weed Book;" W. J. Beal's "The Weeds of Michigan." A list of these publications and where they may be obtained will be found. in the bibliography.

Ames, Iowa, December 18, 1912.

L. H. PAMMEL.