Polytrichum is a genus of mosses — commonly called haircap moss or hair moss — which contains approximately 70 species that cover a cosmopolitan distribution. (Less common vernacular names include bird wheat and pigeon wheat.)The genus Polytrichum has a number of closely related sporophytic characters. The scientific name is derived from the Ancient Greek words polys, meaning 'many', and thrix, meaning 'hair'. This name was used in ancient times to refer to plants with fine, hairlike parts, including ...