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.
Types of Lettuce. In the United States, an 1885 agricultural report listed no fewer than 87 varieties of lettuce. Today, there are four basic types of lettuce: butterhead, iceberg, loose leaf, and romaine. You are likely to find all of these in the produce sections of most supermarkets. Butterhead lettuce: This type includes Boston and Bibb lettuces, which are characterized by a loose head and grass-green leaves. Both have a soft âbutteryâ texture and a sweet, mild flavor. A head of Boston lettuce resembles a flowering rose. Bibb lettuceâalso called limestoneâforms a smaller, cup-shaped head.