Asplenium trichomanes ssp. trichomanes gametophyte. A light and electron microscope study

In controlled culture conditions Asplenium trichomanes L. ssp. trichomanes spores germinate 8–10 days after sowing. The first protonemal cell and the primary rhizoid arise from two unequal divisions of the original spore cell. First an unbranched 5–6-celled germ forms which later becomes a spatula-, racket- and finally heart-shaped, bisexual prothallus with archegonia consisting of four rows of four cells and antheridia consisting of opercular, ring and basal cells. An additional notch with associated archegonia and antheridia develops in several-month-old gametophytes. The ultrastructure of the mature gametophyte is characterized by pleomorphic mitochondria, plastids which may be chloroamyloplasts, vacuoles containing osmiophilic materials and poorly developed endoplasmic reticulum of smooth type. The walls are crossed by many plasmodesmata. (Membrane) structures are visible inside the wall materials nearest the plasmalemma. © 1995 Taylor & Francis Group, LLC.