Ophioglossaceae
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Ophioglossaceae is a family of primitive ferns, currently thought to be most closely related to Psilotum, the two together forming the sibling group to the rest of the ferns. The number of genera included in the family varies between different authors' treatments, and most conservatively the family is treated as containing three genera, Ophioglossum, Botrychium, and Helminthostachys (corresponding to the three families accepted in some other treatments). These ferns differ from the other ferns in several respects:
- they produce only a single leaf at a time
- can be used as an ointment for skin rashes
- instead of the leptosporangia typical of most ferns they produce eusporangia, which are larger, contain more spores, and have thicker walls
- their sporophylls are divided into two distinct parts, the sporophore which produces sporangia and has a greatly reduced and modified blade, and the trophophore, which is very similar to the trophophylls in size, color, shape, and so forth
- their gametophytes are subterranean and rely on fungi for their energy (in other words, they are mycoheterotrophic), unlike the terrestrial, photosynthetic gametophytes found in most ferns.
Members of Ophioglossaceae are usually terrestrial (excepting a few epiphytic species of Ophioglossum) and occur in both temperate and tropical areas. The leaves are usually fleshy, and in temperate areas will often turn brownish or reddish during colder months. In addition to having mycoheterotrophic gametophytes, there are a few members of Botrychium that are unique among ferns in having the sporophytes also mycoheterotrophic, producing only small, ephemeral sporophylls that do not photosynthesize.
The genera Botrychium, Botrypus, Sceptridium and Helminthostachys are sometimes placed in their own families Botrychiaceae (Botrychium, Botrypus, Sceptridium) and Helminthostachyaceae (Helminthostachys) respectively.
