x PREFACE 
the only tools which can be used effectively — as the writer knows 
by many years of hard practical experience, both in garden and 
in field. Again, some simple expedient of little cost and easy 
application, may do the work of many hands and increase by 
many fold the soil’s return for the labor. A wider acquaintance 
with such methods of control seems desirable and therefore the 
writer has endeavored to bring together, so far as could be learned, 
the knowledgé gained by much study and careful experiment in 
many different parts of the country by earnest and thought- 
ful workers. There is a great dearth of books on this most. im- 
portant subject, but such as could be obtained have been diligently 
studied. The Bibliography on page 559 will indicate the writer’s 
debt in this regard. Many files of agricultural periodicals have 
been consulted and most grateful acknowledgment is made for 
assistance received from the publications of the Department of 
Agriculture at Washington, and to the Agricultural Experiment 
Station Bulletins of the various states and of the Canadian 
Provinces. 
In nomenclature and order of classification the writer has fol- 
lowed Gray’s New Manual of Botany, seventh edition, 1908. For 
plants outside of the geographic limits included in that book, 
Coulter and Nelson’s New Manual of Rocky Mountain Botany, and 
W. L. Jepson’s Flora of Western Middle California, have been con- 
sulted. For range, season of bloom and fruit, and much other very 
important and necessary information, most invaluable help has 
been obtained from the New Illustrated Flora of the Northern 
United States and Canada, by Britton and Brown, and the revised 
Flora of the Southeastern United States, by Dr. J. K. Small. 
Statements concerning plants that are poisonous or otherwise harm- 
ful to health have been made on authority of publications issued by 
the United States Department of Agriculture. Dr. L, H. Pammel’s 
Manual of Poisonous Plants has also been a helpful reference. 
Mention is made of the fact that some weeds are medicinally valu- 
able, and may occasionally be made to pay for the cost of their 
extermination. The writer’s authority for prices and modes of 
preparation has been the interesting series of bulletins prepared by 
Miss Alice Henkel, Assistant, Drug-Plant Investigations, at the 
Bureau of Plant Industry at Washington. 
