The fronds of tree ferns are usually very large and multiple-pinnated, but at least one type has entire (undivided) fronds. The fronds of tree ferns also exhibit circinate vernation, meaning the young fronds emerge in coils that uncurl as they grow.he order Cyatheales, which includes the tree ferns, is a taxonomic division of the fern class, Polypodiopsida.
rap noun (MUSIC) A2 [ U ] a type of popular music with a strong rhythm in which the words are spoken, not sung:
rap music. 1. a style of popular music, developed by disc jockeys and urban blacks in the late 1970s, in which an insistent, recurring beat pattern provides the background and counterpoint for rapid, slangy, and often boastful rhyming patter glibly intoned by a vocalist or vocalists. Also called rap.