fern prothallium (prothallus)

antheridium archegonium biology botanical botany brown close closeup darkfield detail education educational enlarge enlarged female fern frame full gametophyte germination green illumination light macro magnification magnify male micrograph microphotograph microphotography microscope microscopic microscopy nobody one organism organs plant propagation prothallium prothallus rhizoid rhizoids science scientific sex transmitted upward view yellow