Reboulia

Terrestrial or on thin soil over rocks, monoicous or rarely dioicous. Thallus dichotomously forking at apex forming patches or diffuse rosettes, yellow green or light green, becoming purple to black at margins, glabrous, without adaxial grooves; margins undulate, becoming incurved when dry. Photosynthetic tissue divided vertically into several irregular tiers of air chambers, occupying around half thickness of thallus along midline; specialised air pores surrounded by 3–6 concentric rings of cells, not elevated above adjacent adaxial thallus. Oil cells present in storage tissue and abaxial scales. Abaxial scales in 2 rows, conspicuous, lunate, with 1–4 linear appendages, purple, with marginal slime papillae. Adaxial epidermis persistent, hyaline, collenchymatous, unistratose. Androecia sessile, irregular, elliptic to lunate cushions, warty, near apical notch, occasionally encircled by minute purple scales. Archegoniophore arising from apical notch; stalk to c. 25 mm tall, with air chambers, with a single rhizoid furrow, with linear scales at base and apex; carpocephalum 4–7-lobed, convex and with complex air pores adaxially; pseudoperianth absent; capsule dehiscence by a decaying lid, unistratose; elaters 2–3-spiral. Spores tetrahedral with prominently winged margins, areolate, yellowish brown; proximal face with triradiate mark.