Life history of A. major/L. rhyniensis showing stages in the development of the dimorphic gametophytes. The mature sporophyte (lower left) bears sporangia with spores of two types. Blue spores develop into mature antheridiophores; orange spores develop into archegoniophores.

Rhynie chert plants. (A–L) Lyonophyton. (P) Horneophyton. (O) Remyophyton.(Q) Aglaophyton.(A) Spore before germination with conspicuous trilete mark. (Scale bar, 15 μm.) (B) Early stage in gametophyte development showing initial transverse division (arrow). (Scale bar, 15 μm.) (C) Two-celled stage showing formation of a cross wall (arrow). (Scale bar, 13 μm.) (D) Multicellular gametophyte (arrow) protruding from broken spore coat. (Scale bar, 15 μm.) (E) Polar view of multicellular gametophyte showing arrangement of cells just beneath apical cell. (Scale bar, 15 μm.) (F) Gametophyte showing apical cell (upper arrow) and spore coat remnants (lower arrow). (Scale bar, 15 μm.) (G) Stoma on lower surface of gametangiophore. (Scale bar, 40 μm.) (H) Cortical cells with endomycorrhizal hyphae in intercellular spaces (arrows). (Scale bar, 50 μm.) (I) Cortical cells of gametangiophore containing arbuscules. (Scale bar, 12 μm.) (J) Longitudinal section of several conducting elements. (Scale bar, 7 μm.) (K) Longitudinal section of distal end of antheridiophore with two antheridia (arrows). (Scale bar, 2 mm.) (L) Longitudinal section of antheridium. (Scale bar, 100 μm.) (M) Section of antheridium showing sperm packets. (Scale bar, 5 μm.) (N) Longitudinal section of archegonium showing neck canal (upper arrow) and probable egg chamber (lower arrow). (Scale bar, 40 μm.) (O) Dense cluster of gametophytes showing size of antheridiophores and archegoniophores. (Scale bar, 6.5 mm.) (P) Spore aggregate. (Scale bar, 1.0 mm.) (Q) Bulbil (arrow) on vegetative axis. (Scale bar, 1.0 mm.)