Science Fair Project Encyclopedia
|Families and Genera|
The Ophioglossophyta are a small group of plants. Traditionally they are included in the division Pteridophyta, the ferns, originally as a family and later as the order Ophioglossales. However, it is now recognized that this group is wholly distinct from the ferns and apparently from the other extant groups of plants. Thus they may be given a separate division, called the Ophioglossophyta. One scheme groups them with the horsetails and whisk ferns in the division Archeophyta .
The two principal families of ophioglossoids are the adders-tongues, Ophioglossaceae, and the moonworts and grape-ferns, Botrychiaceae. Many workers still place the moonworts in the Ophioglossaceae, along with the distinct species Helminthostachys zeylanica. Other times, this species is given its own family Helminthostachiaceae .
All the ophioglossoids have short-lived spores formed in sporangia lacking an annulus, and borne on a stalk that splits from the leaf blade; and fleshy roots. Many species only send up one frond or leaf-blade per year. A few species send up the fertile spikes only, without any conventional leaf-blade. The gametophytes are subterranean. The spores will not germinate if exposed to sunlight, and the gametophyte can live some two decades without forming a sporophyte.
The genus Ophioglossum has the highest chromosome counts of any known plant.
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