It is easy to understand the relation of the saprophytic and the holophytic Flagellates to true plants.
Radial (monaxial) forms; nutrition saprophytic or holophytic, mostly one flagellate.
holophytic hol·o·phyt·ic (hŏl'ō-fĭt'ĭk, hō'lō-)
Not requiring the ingestion of exogenous organic substances for nutrition; obtaining nourishment in the manner of a green plant. Used of certain protozoans capable of photosynthesis.