Pachymeniopsis shinchonai M.Y. Yang et M.S. Kim, 2025

Figure 2: External morphology of Pachymeniopsis shinchonai M.Y. Yang et M.S. Kim sp.nov. (A–C) In situ habit of plants growing at Shinchon,Jeju Island, showing young plant collected February 13, 2024 (A), densely arranged thallus becoming hemispherical in form, collected July 6, 2024 (B), fertile plant collected November 27, 2023 (C). (D) A partial thallus detached from the mass showing dichotomous to sub-dichotomous branching pattern, collected February 13,2024.(E) Ventral view of hemispherical thallus collected July 6,2024.(F) Dorsal view of hemispherical thallus collected July 6,2024.(G) Ventral view of thallus showing a main holdfast (arrow), collected August 22, 2024. (H) Ventral view of thallus showing two holdfasts (arrows) and several secondary attachments (arrowheads),collected August 22,2024.(I–K) Branches adhering to adjacent branches by secondary attachments (arrows).Scale bars = 2 cm (A–C, F, G), 1 cm (D–E, H), and 0.2 cm (I–K).

Figure 3: Vegetative structure and development of tetrasporangia of Pachymeniopsis shinchonai M.Y. Yang et M.S. Kim sp. nov. (A) Transverse section through a young branch showing the cortex and medulla.(B) Detail of cortex showing cellular cortex composed of five-cells and a network of stellate inner cortical cells. Note secondary pit-connections appear between adjacent cortical cells (arrows). (C) Longitudinal section through a young branch showing entangled tubular medullary cells with numerous branches (arrows).(D) Transverse section through middle part of a thallus showing enlarged sub-cortex and densely filled medulla.(E) Transverse section through basal part of a thallus showing a thickened cortex and dense medulla.(F) Cortexof basal part of a thallus showing a thickened cortex composed of six to seven cell layers. (G) Tetrasporangia restricted to the proliferations (arrows). (H) Tetrasporangia initial (arrow) born laterally on inner cortical cell (arrowhead) connected by pit connection (pc). (I) A transverse division of developed tetrasporangium (arrow), which is basally connected to inner cortical cell (arrowhead) by pit connection (pc). (J) Cruciately divided tetrasporangium (arrow), still basally connected to inner cortical cell. Scale bars = 60 µm (A), 40 µm (B, I), 50 µm (C, F), 100 µm (D, E), 1 mm (G), and 20 µm (H, J).

Figure 4: Female reproductive structure of Pachymeniopsis shinchonai M.Y. Yang et M.S. Kim sp. nov. (A) Cystocarp-bearing proliferations (arrows) showing circular to widely expanded shapes. (B) Two-celled carpogonial branch composed of a carpogonium (cp) with a long trichogyne (tr), and hypogenous cell (hy) borne on an elongated cortical cell (arrow).(C) Auxiliary cell ampulla showing the four-celled stage of a first-order ampullar filament (af1) borne on an elongated cortical cell (arrow). (D) Further development of first-order (af1, labeled 1–7) and second-order (af2, labeled 1′–6′) ampullar filaments.(E) A later stage showing the third-order filament (af3) and auxiliary cell (aux). (F) Early post-diploidization showing the auxiliary cell (aux) and three ampullar filaments (af1–af3), which bear branches of each of the ampullar filaments (arrowheads).(G). A later stage of (F) showing the auxiliary cell (aux) enclosed by ampullar filaments (af1–af3) and numerous branches of the ampullar filaments (arrowheads).Note secondary medullar filaments (smf) surrounding the whole cystocarp. (H). Highly branched ampullar filaments and remnants of secondary medullar filaments (smf) surrounding the cystocarp. (I) Carposporophyte showing the gonimoblast initial (gi) producing gonimoblasts (g) and formation of fusion cell (fc). Note remaining branched ampullar filaments (arrowheads) and secondary medullar filaments (smf) forming the pericarp. (J) Gonimoglobes (g1, g2) differentiating into carposporangia and remains of secondary medullar filaments (smf) forming the pericarp.Scale bars = 1 mm (A), 20 µm (B, C,E–H), 10 µm (D), and 40 µm (I, J).