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.
Noun. 1. head lettuce-distinguished by leaves arranged in a dense rosette that develop into a compact ball. Lactuca sativa capitata. butterhead lettuce-lettuce with relatively soft leaves in a loose head; easily broken or bruised.crisphead lettuce, iceberg lettuce, iceberg-lettuce with crisp tightly packed light-green leaves in a firm head; iceberg is still the most popular lettuce.genus Lactuca, Lactuca-an herb with milky juice: lettuce; prickly lettuce. lettuce-any of various plants of the genus Lactuca.oun. 1. head lettuce-distinguished by leaves arranged in a dense rosette that develop into a compact ball. Lactuca sativa capitata. butterhead lettuce-lettuce with relatively soft leaves in a loose head; easily broken or bruised.