Aytoniaceae

Perennial, terrestrial or lithophytic, monoicous or rarely dioicous with male and female plants similar size. Specialised asexual propagules absent. Plants comprising a simple or dichotomously or occasionally abaxially branching thallus. Thallus much thicker near midrib, differentiated into tissue composed of walls of photosynthetic cells that bound air chambers adaxial to solid tissue dedicated to storage, glaucous green, bright green or lime-green, glabrous, without adaxial grooves; margins crenate or undulate; air chambers not floored by free photosynthetic filaments, in a single layer (not in Victoria) or multiple tiers, defined by polygonal boundaries on adaxial surface, often partially subdivided by supplementary partitions, thicker to not as thick as underlying storage tissue; adaxial epidermal thallus mostly lacking chloroplasts, usually firm and persistent, rarely delicate and fissuring with age (not in Victoria), thin to thick-walled, with or without trigones; air pores simple, surrounded by 1–6 rings of differentiated or sometimes scarcely differentiated cells. Abaxial scales conspicuous in 2 rows, ovate or triangular to lunate, with 1–4 triangular, lanceolate, ovate, orbicular or linear appendages, purple, reddish or black. Oil cells usually in storage tissue and abaxial scales, sometimes also in adaxial epidermis and among photosynthetic cells bounding air chambers. Rhizoids present, without and with internal peg-like thickenings, between abaxial scales or along abaxial midline. Androecia patches of papillae or discrete reniform, elliptic or circular cushions at the growth apex or on adaxial surface; cushions surrounded by subulate scales. Sporophytes elevated above thallus on archegoniophore; archegoniophore comprising a stalk and carpocephalum, arising at growing apex or on adaxial midline away from margin; stalk with or without hair-like scale at base and apex, with or without air chambers, with 1 rhizoid furrow or without rhizoid furrow; carpocephalum campanulate or hemispheric, with 1–5 lobes each abaxially with one sporophyte, or discoid and unlobed (not in Victoria), with compound air pores adaxially; involucre bilabiate or entire and campanulate; pseudoperianth pleated and conic, splitting into linear segments but often remaining apically connate, or absent. Seta short. Capsule globose, dehiscence by a regular (not in Victoria) or decaying lid, unistratose or bistratose apically (not in Victoria); elaters present, 1–5-spiral. Spores tetrahedral, usually with prominently winged margins, yellow, orange-yellow, brown, purple (not in Victoria), red-brown (not in Victoria) or black (not in Victoria); areolate or with prominent sinuate ridges (not in Victoria) and with or without (not in Victoria) triradiate mark on proximal face.