| Noun | 1. | Heterotrichales - yellow-green algae with simple or branching filaments; comprising the single family Tribonemaceae protoctist order - the order of protoctists Chrysophyta, division Chrysophyta - mostly freshwater eukaryotic algae having the chlorophyll masked by brown or yellow pigment; yellow-green and golden-brown algae and diatoms: Xanthophyceae, Chrysophyceae, Bacillariophyceae; some classification systems superseded or subsumed by Heterokontophyta family Tribonemaceae, Tribonemaceae - simple filamentous freshwater yellow-green algae |