Conductors and Insulators. In a conductor, electric current can flow freely, in an insulator it cannot. Metals such as copper typify conductors, while most non-metallic solids are said to be good insulators, having extremely high resistance to the flow of charge through them.onductors and Insulators. In a conductor, electric current can flow freely, in an insulator it cannot. Metals such as copper typify conductors, while most non-metallic solids are said to be good insulators, having extremely high resistance to the flow of charge through them.
Butterhead lettuce. A type of head lettuce whose botanical name is Lactuca sativa var. heirloom. Two common types are Boston and bibb lettuce. Have small, round, loosely formed heads with soft, buttery-textured leaves ranging from pale green on the outer leaves to pale yellow-green on the inner leaves.
Dark green leaf lettuce is high in folate and fiber. Dark green vegetables are a subgroup of the vegetable food group, one of five main food groups established by the U.S. Department of Agriculture to promote healthy eating.alad Greens. Dark leafy salad greens, including leaf lettuce and non-lettuce greens, make up a significant portion of the dark green vegetable subgroup. Varied in texture and flavor, these mostly non-bitter greens are typically used in fresh salads.