Blechnum blechnoides photo: John BarklaTrue or leptosporangiate ferns account for more than half of all ferns with between 11,000 and 12,000 taxa worldwide. This makes them the most diverse group of living land plants after flowering plants. They are characterised by having sporangia that arise from a single epidermal cell. Typically, the sporangium is also covered by an indusium although this may be much reduced
For more information see:
- Leptosporangiate ferns by Kathleen M. Pryer, Alan R. Smith and Carl Rothfells
- Leptosporangiate fern (Wikipedia)