blue-green alga

blue-green alga \blue"-green al"ga\ pl. {blue"-green al"gae}
   [from the color and resemblance to algae.]
   any of a group of photosynthetic microorganisms possessing
   characteristics of both bacteria and plants. When classed as
   bacteria, they are assigned to the Cyanobacteria; when
   classed as plants, they are assigned to the Cyanophyta. They
   are now known to be prokaryotic, and are usually called
   {cyanobacteria} in technical contexts. See {cyanobacterium}.
   [PJC]