Manuscripts on the biology, physiology, or control of weeds, and on herbicides, growth regulators, or related topics will be considered for publication in Weed Science. Each manuscript must contain original material constituting a logical unit of related subject matter and must contribute to the advancement of knowledge. Acceptance is made with the understanding that the substance of the manuscript has not been and will not be published elsewhere other than as an abstract. Progress reports, unreplicated experiments, or simple observational information are not acceptable. Most experiments should be repeated in time or space and must provide confirming results. If repeated experiments do not provide confirming results, additional research may be required to determine why. Use objective measurements of responses; visual assessments are generally acceptable only as supportive evidence.