Blue-green algae. Coloured scanning electron micrograph (SEM) of the filamentous blue-green alga, Lyngbya sp. Elongated strands made up of rows of cells are seen, with each strand called a trichome. The cells of Lyngbya have a protective sheath, visible at the end of a cell at the lower left corner. The strands fragment to form shorter chains of cells called hormogonia. Lyngbya is a common filamentous blue-green algae occurring widely in marine and freshwater environments, and in mangrove swamps. Blue-green algae (Cyano- bacteria) are among the most primitive forms of life. Magnification: x600 at 5x7cm size. x2100 at 10x7"~LANDSCAPE"