Although usually romaine lettuce leaves are very flat, sometimes they are somewhat crinkled as well. Avoid romaine lettuce leaves that are wilted or that feel too thick and leathery to the touch. Romaine lettuce can sometimes get very leathery and usually has little flavor when it is thick, tough and leathery. Don't bother with the so-called 'romaine hearts' where the most nutritious part of the romaine lettuce head has been stripped off.
Romaine Lettuce Leaves - unusually crinkly and voluminous