An account of the structure of plants naturally begins with the cell which is the proximate unit of organic structure. The elementary unit of plant structure, as of animal structure, is the cell. Faunistically, although not geographically, the Nearctic and Palaearctic areas must form the two subdivisions of one great unit, for which the  Holarctic region  is now the generally accepted term.
Definition: a subclass considered a phylum of the kingdom Protista in some classifications; includes holozoic or saprozoic flagellates.
The cilia and flagella are made of protein filaments that are  called microtubules doublets. These microtubules doublets are  hollow cylinders.es A flagellum, also called undulipodium, is a whip-like structure used for locomotion, for feeding or other purposes. Almost all organisms have flagella to include protozo â¦ a (at some stage in their lives). We humans have them in our bodies. Even our own spermatozoa can be regarded as flagellates.