Duane Isely

"The seeds of a few kinds of weeds can be carried long distances by natural means; for instance, dandelion seeds are wind-transported, cockleburs and stickseeds are carried by the hair of animals. However, the seeds of most weeds are spread by human agencies, most commonly in mixtures with agricultural seed."

"Legumes are vital because they provide fixed nitrogen for agricultural soils (the recent substitution of synthetic nitrogen fertilizers certainly being a temporary expedient), and because they furnish most of the protein for human food in high-population parts of the world. Man's dependence on grasses and legumes has been coeval."