Botany picture #22: Osmunda regalis

Osmunda regalis (Osmundaceae), Botanic Garden of the University of Halle, Germany, 2008. The Osmundaceae are a small but very interesting family of ferns. They are an old group and possibly the sister clade to all other leptosporangiate ferns. The family was apparently more abundant in the Mesozoic than today as documented by a fairly good fossil record.

Many species are very large and robust compared to other ferns, and their large fronds often have specialized pinnae carrying the sporangia; in most other leptosporangiate ferns, the sporangia are found either on otherwise normal pinnae or an entire frond is turned into a specialized sporophyll. In the case of this European species, the apex of the frond carries the sporangia and is visibly different from the lower pinnae. The next botany picture will show a species with a different arrangement.