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:
Rip Rap. Definition: Riprap â also known as rip rap, rubble, shot rock or rock armour â is rock or other material used to armor shorelines, streambeds, bridge abutments, pilings and other shoreline structures against scour, water or ice erosion.ip Rap. Definition: Riprap â also known as rip rap, rubble, shot rock or rock armour â is rock or other material used to armor shorelines, streambeds, bridge abutments, pilings and other shoreline structures against scour, water or ice erosion.