xii PREFACE 



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 in- 

 debted 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 Michi- 

 gan bulletin, and to the Nevada Station for the use of the Hill- 

 man 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 sev- 

 eral textbooks of botany, as the Bergen & Davis book published by 

 Ginn & Co.; several botanical works like Thome's published in 

 German, and to the Connecticut Experiment Station. A few fig- 

 ures 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. Qutade. The clerical work of the volume was per- 

 formed 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 edi- 

 torial 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 "AVeeds of 

 the Farm and Garden," a general treatise of three hundred pages 



