The shoots of haircap moss obtain nitrogen from soil via water-conducting tissues called hydroids.
“Polytrichum alpinum [Polytrichastrum alpinum] (class Polytrichospida) is predominantly endohydric, transporting water up from underlying substrate by means of water-conducting hydroids (Longton 1988; Buck & Goffinet 2000), whereas Racomitrium lanuginosum (class Bryopsida) is ectohydric and mostly absorbs water from precipitation (Proctor 1982; Buck & Goffinet 2000).” (Ayres et al. 2006:286)