Seeds, as small and unobtrusive as they seem, are an essential part of the life cycle of plants. In addition, they are useful for indentification of plants and, in fact, are often superior for that purpose that other parts of a plant. Thant's because seedds have distinctive characteristics, tend to outlast all other plant parts, and vary little within a species-unlike other parts such as leaves. Since weeds interfere with the growth, harvesting, and quality of crops, Linda Dvais says, the ability to identify weed seeds before they are indavertently planted affords an economic advantage. Other...