Practice question

Conducting tissues in bryophytes show functional analogues convergently resembling xylem and phloem despite lacking lignin. Polytrichopsida and many Bryopsida mosses like Polytrichum commune, Mnium undulatum develop central stem strand containing specialized cells: hydroids elongated dead thin-walled cells lacking lignin conducting water via capillary flow and pits, and leptoids living elongated cells with plasmodesmata transporting assimilates resembling sieve elements of phloem. Liverworts and hornworts generally lack differentiated hydroids or leptoids, relying on external conduction. Evolution of these tissues indicates independent origin of long-distance transport.