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.
Salad 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.ooking Greens. Swiss chard, kale, bok choy, collards and mustard, beet and turnip greens are common dark leafy cooking greens, vegetables that are distinguished by their high concentration of nutrients and pungent flavor.