Fluorescence micrograph of a transverse section of a hornwort (Anthoceros agrestis) thallus with antheridia. The gametophyte cells each have a single chloroplasts inside. The presence of one chloroplast per cell is a unique feature in land plants and hornworts share it with green algae the progenitors of land plants. Plant tissue is observed in ultraviolet (UV) light. Magnification: x300 when printed at 10 x 10 cm.