Ophioglossales
Encyclopedia
Ophioglossales are a small group of pteridophyte
plant
s. Traditionally they are included in the division Pteridophyta, the fern
s, 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
.
Ophioglossales contains a single family, Ophioglossaceae, which in some classifications is sometimes split into two or three families, the adders'-tongues
, Ophioglossaceae
, and the moonwort
s 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 spore
s formed in sporangia
lacking an annulus, and borne on a stalk that splits from the leaf blade; and fleshy root
s. 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 gametophyte
s 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).
Pteridophyte
The pteridophytes are vascular plants that produce neither flowers nor seeds, and are hence called vascular cryptogams. Instead, they reproduce and disperse only via spores. Pteridophytes include horsetails, ferns, club mosses, and quillworts...
plant
Plant
Plants are living organisms belonging to the kingdom Plantae. Precise definitions of the kingdom vary, but as the term is used here, plants include familiar organisms such as trees, flowers, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The group is also called green plants or...
s. Traditionally they are included in the division Pteridophyta, the fern
Fern
A fern is any one of a group of about 12,000 species of plants belonging to the botanical group known as Pteridophyta. Unlike mosses, they have xylem and phloem . They have stems, leaves, and roots like other vascular plants...
s, 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
Psilotopsida
Psilotopsida is a class of fern-like plants. It should not be confused with the obsolete class Psilophytopsida. As circumscribed by Smith et al. Psilotopsida contains two families, Psilotaceae and Ophioglossaceae, placed in orders Psilotales and Ophioglossales, respectively...
.
Ophioglossales contains a single family, Ophioglossaceae, which in some classifications is sometimes split into two or three families, the adders'-tongues
Ophioglossum
Ophioglossum is a genus of about 25-30 species of Ophioglossales in the family Ophioglossaceae, with a cosmopolitan but primarily tropical and subtropical distribution. The name Ophioglossum comes from the Greek, and means "snake-tongue".Adders-tongues are so-called because the spore-bearing stalk...
, Ophioglossaceae
Ophioglossaceae
Ophioglossaceae, the Adder's tongue family, is a family of ferns, currently thought to be most closely related to Psilotaceae, the two together comprising the class Psilotopsida as the sibling group to the rest of the ferns. The Ophioglossaceae is one of two groups of ferns traditionally known as...
, and the moonwort
Moonwort
Moonworts are ferns, seedless vascular plants, of the genus Botrychium, sensu stricto. They are small, with fleshy roots, and reproduce by spores shed into the air. One part of the leaf, the trophophore, is sterile and fernlike; the other, the sporophore, is fertile and carries the clusters of...
s and grape-ferns, Botrychiaceae
Botrychiaceae
Botrychiaceae is a segregate family of ferns. The family includes the genera Botrychium , Botrypus , and Sceptridium...
. The distinct species Helminthostachys zeylanica is sometimes given its own family, Helminthostachyaceae. A recently-discovered species and new genus, Mankyua
Mankyua
Mankyua is a recently-discovered plant, a single species in its own genus. It is a fern in the Ophioglossales. Its only species, M. chejuense , grows only on a small Korean island, Cheju Island....
chejuense, makes the picture more complicated. Most recent treatments of the Ophioglossoids have treated all of them in Ophioglossaceae.
The plants have short-lived spore
Spore
In biology, a spore is a reproductive structure that is adapted for dispersal and surviving for extended periods of time in unfavorable conditions. Spores form part of the life cycles of many bacteria, plants, algae, fungi and some protozoa. According to scientist Dr...
s formed in sporangia
Sporangium
A sporangium is an enclosure in which spores are formed. It can be composed of a single cell or can be multicellular. All plants, fungi, and many other lineages form sporangia at some point in their life cycle...
lacking an annulus, and borne on a stalk that splits from the leaf blade; and fleshy root
Root
In vascular plants, the root is the organ of a plant that typically lies below the surface of the soil. This is not always the case, however, since a root can also be aerial or aerating . Furthermore, a stem normally occurring below ground is not exceptional either...
s. Many species only send up one frond
Frond
The term frond refers to a large, divided leaf. In both common usage and botanical nomenclature, the leaves of ferns are referred to as fronds and some botanists restrict the term to this group...
or leaf
Leaf
A leaf is an organ of a vascular plant, as defined in botanical terms, and in particular in plant morphology. Foliage is a mass noun that refers to leaves as a feature of plants....
-blade per year. A few species send up the fertile spikes only, without any conventional leaf-blade. The gametophyte
Gametophyte
A gametophyte is the haploid, multicellular phase of plants and algae that undergo alternation of generations, with each of its cells containing only a single set of chromosomes....
s are subterranean. The spores will not germinate if exposed to sunlight, and the gametophyte can live some two decades without forming a sporophyte
Sporophyte
All land plants, and some algae, have life cycles in which a haploid gametophyte generation alternates with a diploid sporophyte, the generation of a plant or algae that has a double set of chromosomes. A multicellular sporophyte generation or phase is present in the life cycle of all land plants...
.
The genus Ophioglossum
Ophioglossum
Ophioglossum is a genus of about 25-30 species of Ophioglossales in the family Ophioglossaceae, with a cosmopolitan but primarily tropical and subtropical distribution. The name Ophioglossum comes from the Greek, and means "snake-tongue".Adders-tongues are so-called because the spore-bearing stalk...
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).