moss
蘚 centers on moss: small, soft green plants that grow in dense clumps or mats in damp or shady locations.
蘚 is a phono-semantic compound: the grass radical 艹 indicates a plant, and 鮮 (セン) gives the sound. The character originally referred to moss.
The top 艹 shows it's a plant. The bottom 鮮 suggests something fresh or vivid, like the bright green of moss. Imagine fresh, vivid green moss covering a rock.
For セン, picture a thousand (千, せん) tiny moss plants covering a stone: 千 -> セン, and the moss spreads like a green carpet.
luminous moss
sphagnum; peat moss; bog moss
moss; bryophyte
bryology
bryophyte (any of three groups of non-vascular land plants, incl. mosses, hornworts and liverworts)
mosses (non-vascular plants of class Bryopsida)
Climacium japonicum (species of moss)