Ophioglossales
| Ophioglossales | |
|---|---|
 | |
| Botrychium lunaria | |
| Scientific classification | |
| Kingdom: | Plantae |
| Division: | Pteridophyta |
| Class: | Psilotopsida |
| Order: | Ophioglossales Link |
| Families and Genera | |
| |
Ophioglossales (lit. 'snake-tongue [plants]') are a small group of pteridophyte plants. Traditionally they are included in the division Pteridophyta, the ferns, originally as a family and later as the order Ophioglossales. In some classifications this group is placed in a separate division, the Ophioglossophyta, but recent molecular systematic studies have shown the Ophioglossales to be closely related to the Psilotales. The most recent classification by Smith et al. (2006) places these two orders together in class Psilotopsida.[1]
Ophioglossales contains a single family, Ophioglossaceae, which in some classifications is sometimes split into two or three families, the adders'-tongues, Ophioglossaceae, and the moonworts and grape-ferns, Botrychiaceae. The distinct species Helminthostachys zeylanica is sometimes given its own family, Helminthostachyaceae. A recently discovered species and new genus, Mankyua chejuense, makes the picture more complicated. Most recent treatments of the Ophioglossoids have treated all of them in Ophioglossaceae.
The plants 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. The record holder is Ophioglossum reticulatum, with about 630 pairs of chromosomes (1260 chromosomes per cell).[2]
References and external links
- ↑ Smith, Alan R.; Kathleen M. Pryer; Eric Schuettpelz; Petra Korall; Harald Schneider; Paul G. Wolf (2006). "A classification for extant ferns" (PDF). Taxon. 55 (3): 705–731. doi:10.2307/25065646. JSTOR 25065646.
- ↑ Raven, Peter H., Ray F. Evert, & Susan E. Eichhorn, 2005. Biology of Plants, 7th edition. (New York: W. H. Freeman and Company). ISBN 0-7167-1007-2.