Moss. Coloured environmental scanning electron micrograph (ESEM) of an unidentified moss (class Bryopsida). Mosses are simple plants that lack true roots or vascular tissue. They grow in damp places throughout the world. Unlike a conventional scanning electron microscope (SEM), samples placed into an environmental SEM do not need to be desiccated or coated in gold. This is an untreated sample. Magnification unknown.