''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family
Isoetaceae
Isoetaceae is a family including living quillworts (''Isoetes'') and comparable extinct herbaceous lycopsids (''Tomiostrobus
''Tomiostrobus'' is an extinct quillwort genus from the Early Triassic of Australia, China and Russia, which was espe ...
, which is in the class of
lycopods
Lycopodiopsida is a class of vascular plants known as lycopods, lycophytes or other terms including the component lyco-. Members of the class are also called clubmosses, firmosses, spikemosses and quillworts. They have dichotomously branching s ...
. There are currently 192 recognized species, with a
cosmopolitan distribution
In biogeography, cosmopolitan distribution is the term for the range of a taxon that extends across all or most of the world in appropriate habitats. Such a taxon, usually a species, is said to exhibit cosmopolitanism or cosmopolitism. The ext ...
but with the individual species often scarce to rare. Some
botanist
Botany, also called , plant biology or phytology, is the science of plant life and a branch of biology. A botanist, plant scientist or phytologist is a scientist who specialises in this field. The term "botany" comes from the Ancient Greek wo ...
s split the genus, separating two South American species into the genus ''Stylites'', although molecular data place these species among other species of ''Isoetes'', so that ''Stylites'' does not warrant taxonomic recognition. Species of ''Isoetes'' virtually identical to modern forms have existed since the
Jurassic
The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately Mya. The J ...
epoch.
The name of the genus may also be spelled ''Isoëtes''. The diaeresis (two dots over the e) indicates that the o and the e are to be pronounced in two distinct syllables. Including this in print is optional; either spelling (''Isoetes'' or ''Isoëtes'') is correct.
Description
Quillworts are mostly aquatic or semi-aquatic in clear ponds and slow-moving streams, though several (e.g. '' I. butleri'', '' I. histrix'' and '' I. nuttallii'') grow on wet ground that dries out in the summer. The quillworts are spore-producing plants and highly reliant on water dispersion. Quillworts have different ways to spread their spores based on the environment. Quillwort
leaves
A leaf (plural, : leaves) is any of the principal appendages of a vascular plant plant stem, stem, usually borne laterally aboveground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", wh ...
are hollow and quill-like, with a minute
ligule A ligule (from "strap", variant of ''lingula'', from ''lingua'' "tongue") is a thin outgrowth at the junction of leaf and leafstalk of many grasses (Poaceae) and sedges. A ligule is also a strap-shaped extension of the corolla, such as that of a ...
at the base of the upper surface. arising from a central
corm
A corm, bulbo-tuber, or bulbotuber is a short, vertical, swollen underground plant stem that serves as a storage organ that some plants use to survive winter or other adverse conditions such as summer drought and heat (perennation).
The word ' ...
. Each leaf is narrow, long (exceptionally up to ) and wide; they can be either
evergreen
In botany, an evergreen is a plant which has foliage that remains green and functional through more than one growing season. This also pertains to plants that retain their foliage only in warm climates, and contrasts with deciduous plants, which ...
, winter
deciduous
In the fields of horticulture and Botany, the term ''deciduous'' () means "falling off at maturity" and "tending to fall off", in reference to trees and shrubs that seasonally shed leaves, usually in the autumn; to the shedding of petals, aft ...
, or dry-season deciduous. Only 4% of total biomass, the tips of the leaves, is chlorophyllous.Tropical Alpine Environments: Plant Form and Function /ref>
The roots broaden to a swollen base up to wide where they attach in clusters to a bulb-like, underground
rhizome
In botany and dendrology, a rhizome (; , ) is a modified subterranean plant stem that sends out roots and shoots from its nodes. Rhizomes are also called creeping rootstalks or just rootstalks. Rhizomes develop from axillary buds and grow hori ...
characteristic of most quillwort species, though a few (e.g. '' I. tegetiformans'') form spreading mats. This swollen base also contains male and female sporangia, protected by a thin, transparent covering (''velum''), which is used diagnostically to help identify quillwort species. They are
heterosporous
Heterospory is the production of spores of two different sizes and sexes by the sporophytes of land plants. The smaller of these, the microspore, is male and the larger megaspore is female. Heterospory evolved during the Devonian period from isos ...
. Quillwort species are very difficult to distinguish by general appearance. The best way to identify them is by examining their megaspores under a microscope. Moreover, habitat, texture, spore size, and velum provide features that distinguish Isoëtes taxa. They also possess a vestigial form of secondary growth in the basal portions of its cormlike stem, an indication that they evolved from larger ancestors.
Biochemistry and genetics
Quillworts use
Crassulacean acid metabolism
Crassulacean acid metabolism, also known as CAM photosynthesis, is a carbon fixation pathway that evolved in some plants as an adaptation to arid conditions that allows a plant to photosynthesize during the day, but only exchange gases at night. ...
(CAM) for carbon fixation. Some aquatic species don't have
stoma
In botany, a stoma (from Greek ''στόμα'', "mouth", plural "stomata"), also called a stomate (plural "stomates"), is a pore found in the epidermis of leaves, stems, and other organs, that controls the rate of gas exchange. The pore is bor ...
ta and the leaves have a thick cuticle which prevents CO2 uptake, a task that is performed by their hollow roots instead, which absorb CO2 from the sediment. This has been studied extensively in ''Isoetes andicola''.
CAM
Calmodulin (CaM) (an abbreviation for calcium-modulated protein) is a multifunctional intermediate calcium-binding messenger protein expressed in all eukaryotic cells. It is an intracellular target of the secondary messenger Ca2+, and the bin ...
is normally considered an adaptation to life in arid environments to prevent water loss with the plants opening their stomata at night rather than in the heat of the day. This allows CO2 to enter and minimises water loss. As mostly submerged aquatic plants, quillworts do not lack water and the use of CAM is considered to avoid competition with other aquatic plants for CO2 during daytime.
The first detailed quillwort genome sequence, of '' I. taiwanensis'', showed that there were differences from CAM in terrestrial plants. CAM involves the enzyme
phosphoenolpyruvate carboxylase
Phosphoenolpyruvate carboxylase (also known as PEP carboxylase, PEPCase, or PEPC; , PDB ID: 3ZGE) is an enzyme in the family of carboxy-lyases found in plants and some bacteria that catalyzes the addition of bicarbonate (HCO3−) to phosphoenolp ...
(PEPC) and plants have two forms of the enzyme. One is normally involved in photosynthesis and the other in central metabolism. From the genome sequence, it appears that in quillworts, both forms are involved in photosynthesis. In addition, the time of day of the peak abundance of some of the components of CAM was different from terrestrial plants. These fundamental differences in biochemistry suggests that CAM in quillworts is probably another example of
convergent evolution
Convergent evolution is the independent evolution of similar features in species of different periods or epochs in time. Convergent evolution creates analogous structures that have similar form or function but were not present in the last com ...
of CAM during the more than 300 million years since the genus diverged from other plants. However, they may also be because of differences between life in water and in the air. The genome sequence also provided two insights into its structure. First, genes and repeated non-coding regions were fairly evenly distributed across all the
chromosomes
A chromosome is a long DNA molecule with part or all of the genetic material of an organism. In most chromosomes the very long thin DNA fibers are coated with packaging proteins; in eukaryotic cells the most important of these proteins are ...
. This is similar to genomes of other non-seed plants, but different from the seed plants (
angiosperms
Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek words ('container, vessel') and ('seed'), and refers to those plants th ...
) where there are distinctly more genes at the ends of chromosomes. Secondly, there was also evidence that the whole genome had been duplicated in the ancient past.
Taxonomy
Compared to other genera, ''Isoetes'' is poorly known. The first critical monograph on their taxonomy was published in 1922 and remained a standard reference for decades. Even after studies with cytology, scanning electron microscopy, and chromatography, species are difficult to identify and their phylogeny is disputed. Vegetative characteristics commonly used to distinguish other genera, such as leaf length, rigidity, color, or shape are variable and depend on the habitat. Most classification systems for ''Isoetes'' rely on spore characteristics, which make species identification nearly impossible without microscopy.
Reproduction
Overview
Like all land plants, ''Isoetes'' undergoes an alternation of generations between a diploid sporophyte stage and a sexual haploid gametophyte stage. However, the dominance of one stage over the other has shifted over time. The development of vascular tissue and subsequent diversification of land plants coincides with the increased dominance of the sporophyte and reduction of the gametophyte. ''Isoetes'', as members of the
Lycopodiopsida
Lycopodiopsida is a class of vascular plants known as lycopods, lycophytes or other terms including the component lyco-. Members of the class are also called clubmosses, firmosses, spikemosses and quillworts. They have dichotomously branching s ...
class, are part of the oldest extant lineage that reflects this shift to a sporophyte dominant lifecycle. In closely related lineages, such as the extinct ''
Lepidodendron
''Lepidodendron'' is an extinct genus of primitive vascular plants belonging to the family Lepidodendraceae, part of a group of Lycopodiopsida known as scale trees or arborescent lycophytes, related to Isoetes, quillworts and Lycopodiopsida, lyco ...
'', spores were dispersed by the sporophyte through large collections of sporangia called strobili for wind-based spore dispersal. However, ''Isoetes'' are small heterosporous semi-aquatic plants, with different reproductive needs and challenges than large tree-like land plants.
Description
Like the rest of the Lycopodiopsida class, ''Isoetes'' reproduces with spores. Among the lycophytes, both ''Isoetes'' and the
Selaginellaceae
''Selaginella'' is the sole genus of vascular plants in the family Selaginellaceae, the spikemosses or lesser clubmosses.
This family is distinguished from Lycopodiaceae
The Lycopodiaceae (class Lycopodiopsida, order Lycopodiales) are an o ...
(spikemosses) are
heterosporous
Heterospory is the production of spores of two different sizes and sexes by the sporophytes of land plants. The smaller of these, the microspore, is male and the larger megaspore is female. Heterospory evolved during the Devonian period from isos ...
, while the remaining lycophyte family
Lycopodiaceae
The Lycopodiaceae (class Lycopodiopsida, order Lycopodiales) are an old family of vascular plants, including all of the core clubmosses and firmosses, comprising 16 accepted genera and about 400 known species. This family originated about 380 mil ...
(clubmosses) is
homosporous
In biology, a spore is a unit of sexual or asexual reproduction that may be adapted for dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores form part of the life cycles of many plants, algae, ...
. As heterosporous plants, fertile Isoetes sporophytes produce megaspores and microspores, which develop in the megasporangia and microsporangia. These spores are highly ornate and are the primary way by which species are identified, although no one functional purpose of the intricate surface patterns is agreed upon. The megasporangia occur within the outermost
microphylls
In plant anatomy and evolution a microphyll (or lycophyll) is a type of plant leaf with one single, unbranched leaf vein. Plants with microphyll leaves occur early in the fossil record, and few such plants exist today. In the classical concept of ...
(single-veined leaves) of the plant while the microsporangia are found in the innermost microphylls. This pattern of development is hypothesized to improve the dispersal of the heavier megaspore. These spores then germinate and divide into mega- and micro- gametophytes. The microgametophytes have antheridia, which in turn produce sperm. The megagametophytes have archegonia, which produce egg cells. Fertilization takes place when the motile sperm from a microgametophyte locates the archegonia of a megagametophyte and swims inside to fertilize the egg.
Outside of heterospory, a distinguishing feature of ''Isoetes'' (and ''
Selaginella
''Selaginella'' is the sole genus of vascular plants in the family Selaginellaceae, the spikemosses or lesser clubmosses.
This family is distinguished from Lycopodiaceae (the clubmosses) by having scale-leaves bearing a ligule and by having ...
'') from other
pteridophyte
A pteridophyte is a vascular plant (with xylem and phloem) that disperses spores. Because pteridophytes produce neither flowers nor seeds, they are sometimes referred to as "cryptogams", meaning that their means of reproduction is hidden. Ferns, ...
s, is that their gametophytes grow inside the spores. This means that the gametophytes never leave the protection of the spore that disperses them, cracking the perispore (the outer layer of the spore) just enough to allow the passage of gametes. This is fundamentally different from ferns, where the gametophyte is a photosynthetic plant exposed to the elements of its environment. However, containment creates a separate problem for Isoetes, which is that the gametophytes have no way to acquire energy on their own. ''Isoetes'' sporophytes solve this problem by provisioning starches and other nutrients to the spores as an energy reserve for the eventual gametophytes. Although not a homologous process, this provisioning is somewhat analogous to other modes of offspring resource investment in seed-plants, such as fruits and seeds. The extent to which resources provisioned to the megaspore also support the growth of the new sporophyte is unknown in ''Isoetes''.
Dispersal
Spore dispersal occurs primarily in water (
hydrochory
In Spermatophyte plants, seed dispersal is the movement, spread or transport of seeds away from the parent plant.
Plants have limited mobility and rely upon a variety of dispersal vectors to transport their seeds, including both abiotic vectors, ...
) but may also occur via adherence to animals (
zoochory
In Spermatophyte plants, seed dispersal is the movement, spread or transport of seeds away from the parent plant.
Plants have limited mobility and rely upon a variety of dispersal vectors to transport their seeds, including both abiotic vectors, ...
) and as a result of ingestion (
endozoochory
In Spermatophyte plants, seed dispersal is the movement, spread or transport of seeds away from the parent plant.
Plants have limited mobility and rely upon a variety of dispersal vectors to transport their seeds, including both abiotic vectors, ...
). These are among the reasons suggested for the ornamentations of the spore, with some authors demonstrating that certain patterns seem well-adapted for sticking to relevant animals like waterfowl. Another critical element of dispersal is the observation that in some species of ''Isoetes'', the outer coat of megaspores have pockets that trap microspores, a condition known as synaptospory. Typically, heterospory means that colonization and long-dispersal are more difficult due to the fact that a single spore cannot grow a bisexual gametophyte and thus cannot establish a new population from a single spore as can happen in homosporous ferns. ''Isoetes'' may mitigate this issue via microspores stuck to megaspores, greatly increasing the possibility of successful fertilization upon dispersal.
Species
, ''
Plants of the World Online
Plants of the World Online (POWO) is an online database published by the Royal Botanic Gardens, Kew. It was launched in March 2017 with the ultimate aim being "to enable users to access information on all the world's known seed-bearing plants by ...
'' accepted the following extant species:
*''
Isoetes abyssinica
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with the individual sp ...
'' Chiov.
*''
Isoetes acadiensis
''Isoetes acadiensis'', the Acadian quillwort is a species of quillwort in the Isoetaceae family described by Kott in 1981. It can be found along the shores of lakes, ponds, and rivers in Newfoundland, Nova Scotia, and New Brunswick, as well as i ...
'' Kott
*''
Isoetes aemulans
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with the individual s ...
Isoetes alcalophila
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of Lycopodiopsida, lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with t ...
'' S.Halloy
*''
Isoetes alpina
''Isoetes alpina'', the alpine quillwort, is an aquatic plant in the class Lycopodiopsida, endemic to New Zealand.
Its main habitats are the bottom of lakes, rivers and streams, where it often forms extensive colonies in fine sediments or coarse ...
Isoetes amazonica
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with the individual s ...
Isoetes andicola
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with the individual sp ...
'' (Amstutz) L.D.Gómez
*'' Isoetes andina'' Spruce ex Hook.
*''
Isoetes appalachiana
''Isoetes appalachiana'', commonly known as the Appalachian quillwort (not to be confused with its close relative'' Isoetes engelmannii'', which shares the same common name), is an aquatic pteridophyte that is widely distributed in the eastern U ...
Isoetes asiatica
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with the individual sp ...
'' (Makino) Makino
*''
Isoetes attenuata
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with the individual sp ...
Isoetes biafrana
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with the individual sp ...
'' Alston
*''
Isoetes bischlerae
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with the individual sp ...
'' H.P.Fuchs
*''
Isoetes bolanderi
''Isoetes bolanderi'', or Bolander's quillwort, is a species of quillwort, a type of lycophyte. This aquatic plant is native to high altitude regions of the western United States and southern Alberta. It grows almost entirely underwater in lakes ...
Isoetes boomii
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with the individual s ...
Isoetes brevicula
''Isoetes brevicula'' is a quillwort species native to Western Australia
Western Australia (commonly abbreviated as WA) is a state of Australia occupying the western percent of the land area of Australia excluding external territories. It is ...
Isoetes butleri
''Isoetes butleri'', commonly known as limestone quillwort, is a species of plant in the quillwort family, a member of the lycophyte
The lycophytes, when broadly circumscribed, are a vascular plant (tracheophyte) subgroup of the kingdom Pla ...
Isoetes capensis
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with the individual sp ...
Isoetes caroliniana
''Isoetes caroliniana'', common name Carolina quillwort, is a wetlands plant native to the mountains of Tennessee, North Carolina, Virginia and West Virginia. It is an emergent plant found in lakes and bogs. It is closely related to '' I. ge ...
'' (A.A.Eaton) Luebke is regarded by ''Plants of the World Online'' as a synonym of ''
Isoetes valida
''Isoetes valida'', commonly known as the strong quillwort or true quillwort, is an aquatic lycophyte native to eastern North America. It is found primarily in the Appalachian Mountains from Pennsylvania south to Alabama and Georgia. In addition ...
'', but other sources treat it as a valid species
*'' Isoetes chubutiana'' Hickey, Macluf & W.C.Taylor
*''Isoetes coreana'' Y.H.Chung & H.K.Choi is a synonym of ''
Isoetes sinensis
''Isoetes sinensis'', the narrow quillwort, is a species of plant in the family Isoetaceae.
Information
''Isoetes sinensis'' is native to China and Korea. Its natural habitat is swamps. It is threatened by habitat loss. In China, this species is ...
Isoetes creussensis
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with the individual s ...
Isoetes delilei
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with the individual s ...
'' (Bory) Rothm.
*''
Isoetes dispora
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of Lycopodiopsida, lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with t ...
'' Hickey
*''
Isoetes dixitii
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with the individual s ...
Isoetes durieui
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with the individual sp ...
Isoetes echinospora
''Isoetes echinospora'', also known as spiny quillwort, spiny-spored quillwort or spring quillwort is a species of quillwort in the Isoetaceae family, and is the most abundant species in Canada. It can be found in shallow aquatic environments fro ...
Isoetes ekmanii
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with the individual sp ...
Isoetes engelmannii
''Isoetes engelmannii'' is a species of aquatic plant in the family Isoetaceae. It is referred to by the common names Engelmann's quillwort or Appalachian quillwort (not to be confused with the newly described ''Isoetes appalachiana''), and is th ...
'' A.Braun – Engelmann's quillwort
*''
Isoetes escondidensis
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of Lycopodiopsida, lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with t ...
Isoetes flaccida
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with the individual sp ...
'' Shuttlew. – southern quillwort
*''
Isoetes fluitans
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with the individual sp ...
Isoetes georgiana
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with the individual s ...
Isoetes graniticola
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with the individual sp ...
Isoetes heldreichii
''Isoetes heldreichii'', or Pindus quillwort, is a species of lycopod. It is critically endangered. Some think it extinct as it was last seen in 1885.
Distribution
It is found in Central Greece.
Taxonomy
It was described by Richard Wetts ...
'' Wettst.
*''
Isoetes hemivelata
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with the individual sp ...
Isoetes herzogii
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with the individual sp ...
Isoetes hieronymi
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with the individual sp ...
'' U.Weber
*''
Isoetes histrix
''Isoetes histrix'', the land quillwort, is an aquatic pteridophyte native to the Mediterranean region, northwestern Africa, and the coasts of western Europe northwest to Cornwall. It occurs mainly in temporarily wet habitats, otherwise called v ...
Isoetes howellii
''Isoetes howellii'', or Howell's quillwort, is a species of quillwort, a type of lycophyte. It is an aquatic plant native to North America.
Distribution
Isotes howelii is found in western North America and grows in wet habitats such as vernal ...
'' Engelm. – Howell's quillwort
*''
Isoetes humilior
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with the individual s ...
'' A.Braun
*''Isoetes hyemalis'' D.F.Brunt. is a synonym of '' Isoetes riparia'' var. ''amesii''
*''
Isoetes hypsophila
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with the individual sp ...
Isoetes jamaicensis
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with the individual sp ...
'' Hickey
*''
Isoetes japonica
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with the individual sp ...
Isoetes jejuensis
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of Lycopodiopsida, lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with t ...
Isoetes karstenii
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with the individual sp ...
Isoetes kirkii
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with the individual sp ...
Isoetes laosiensis
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with the individual sp ...
Isoetes melanopoda
''Isoetes melanopoda'' is a species of nonflowering vascular plant belonging to the quillworts in the family Isoetaceae. Its common names include: black-footed quillwort, midland quillwort, and prairie quillwort.
Description
''Isoetes melanopoda' ...
'' J.Gay & Durieu – black-footed quillwort
*''
Isoetes melanospora
''Isoetes melanospora'', commonly known as black-spored quillwort or black-spored Merlin's grass, is a rare and endangered aquatic lycophyte endemic to the U.S. states of Georgia and South Carolina. It grows exclusively in shallow, temporary pool ...
'' Engelm. – black-spored quillwort
*''
Isoetes melanotheca
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with the individual sp ...
Isoetes microvela
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with the individual sp ...
Isoetes mongerensis
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with the individual sp ...
'' E.R.L.Johnson – Monger quillwort
*''
Isoetes montana
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with the individual sp ...
'' U.Weber
*''
Isoetes mourabaptistae
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of Lycopodiopsida, lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with t ...
Isoetes muelleri
''Isoetes muelleri'' is a species of Isoetes, quillwort, a type of lycophyte. This generally Apomixis, apomictic aquatic plant is native to Australia.
Distribution and habitat
It is widespread across all the states and territories of Australia ...
'' A.Braun – Mueller's quillwort
*''
Isoetes naipiana
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with the individual sp ...
'' P.G.Windisch, Lorscheitt. & Nervo
*''
Isoetes nana
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with the individual sp ...
'' J.B.S.Pereira
*''
Isoetes neoguineensis
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with the individual sp ...
Isoetes nigroreticulata
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with the individual sp ...
Isoetes nuttallii
''Isoetes nuttallii'', or Nuttall's quillwort, is a species of quillwort, a type of lycopod. It is native to shallow waters and other wet habitats of western North America from British Columbia to California
California is a state in the W ...
Isoetes olympica
''Isoetes olympica'', the Olympic quillwort, is a flowering plant in the family Isoetaceae. The IUCN has classified the species as critically endangered. It was named by Alexander Braun
Alexander Carl Heinrich Braun (10 May 1805 – 29 March 1 ...
Isoetes organensis
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with the individual sp ...
Isoetes ovata
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with the individual sp ...
'' N.Pfeiff.
*''
Isoetes pallida
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with the individual sp ...
'' Hickey
*''
Isoetes palmeri
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with the individual sp ...
Isoetes perrieriana
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with the individual sp ...
'' Iversen
*''
Isoetes philippinensis
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with the individual sp ...
Isoetes pitotii
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of Lycopodiopsida, lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with t ...
Isoetes prototypus
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with the individual sp ...
'' D.M.Britton & Goltz
*''
Isoetes pseudojaponica
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with the individual sp ...
Isoetes pusilla
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with the individual s ...
'' C.R.Marsden & Chinnock
*''
Isoetes quiririensis
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with the individual sp ...
'' J.B.S.Pereira & Labiak
*''
Isoetes ramboi
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with the individual s ...
Isoetes sabatina
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with the individual sp ...
'' Troìa & Azzella
*''
Isoetes saccharata
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with the individual sp ...
Isoetes saracochensis
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with the individual s ...
'' Hickey
*''
Isoetes savatieri
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with the individual sp ...
'' Franch.
*''
Isoetes schweinfurthii
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with the individual sp ...
Isoetes serracarajensis
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with the individual sp ...
'' J.B.S.Pereira, Salino & Stützel
*''
Isoetes setacea
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with the individual sp ...
'' Lam.
*''
Isoetes sinensis
''Isoetes sinensis'', the narrow quillwort, is a species of plant in the family Isoetaceae.
Information
''Isoetes sinensis'' is native to China and Korea. Its natural habitat is swamps. It is threatened by habitat loss. In China, this species is ...
'' T.C.Palmer – China
*''
Isoetes smithii
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of Lycopodiopsida, lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with t ...
'' H.P.Fuchs
*''
Isoetes spannagelii
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with the individual s ...
Isoetes stevensii
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with the individual sp ...
Isoetes taiwanensis
''Isoetes taiwanensis'' is a species of plant in the family Isoetaceae. It is endemic to Taiwan, and the only species of quillwort there. As other quillworts, it is relatively small, with erect leaves long. It grows submersed in shallow ponds fo ...
Isoetes tegetiformans
''Isoetes tegetiformans'', commonly known as mat-forming quillwort or mat-forming Merlin's grass, is an aquatic lycophyte endemic to the U.S. state of Georgia. It grows exclusively in shallow, temporary pools on granite outcrops, often with only ...
Isoetes tennesseensis
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of Lycopodiopsida, lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with t ...
Isoetes transvaalensis
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with the individual sp ...
'' C.Jermy & Schelpe
*''
Isoetes triangula
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with the individual sp ...
Isoetes truncata
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with the individual sp ...
Isoetes tuerckheimii
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with the individual s ...
Isoetes ulei
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with the individual sp ...
'' U.Weber
*''
Isoetes valida
''Isoetes valida'', commonly known as the strong quillwort or true quillwort, is an aquatic lycophyte native to eastern North America. It is found primarily in the Appalachian Mountains from Pennsylvania south to Alabama and Georgia. In addition ...
'' Clute – Carolina or strong quillwort
*''
Isoetes vanensis
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with the individual sp ...
'' M.Keskin & G.Zare
*''
Isoetes vermiculata
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with the individual sp ...
'' Hickey
*''Isoetes virginica'' N.Pfeiff. is a synonym of ''
Isoetes melanopoda
''Isoetes melanopoda'' is a species of nonflowering vascular plant belonging to the quillworts in the family Isoetaceae. Its common names include: black-footed quillwort, midland quillwort, and prairie quillwort.
Description
''Isoetes melanopoda' ...
'' subsp. ''melanopoda''
*''
Isoetes viridimontana
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with the individual sp ...
Isoetes yunguiensis
''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with the individual sp ...
'' Q.F.Wang & W.C.Taylor
Many species, such as the Louisiana quillwort and the mat-forming quillwort, are
endangered species
An endangered species is a species that is very likely to become extinct in the near future, either worldwide or in a particular political jurisdiction. Endangered species may be at risk due to factors such as habitat loss, poaching and inv ...
. Several species of ''Isoetes'' are commonly called Merlin's grass, especially '' I. lacustris'', but also the endangered species '' I. tegetiformans''.
Evolution
Fossilised specimens of '' I. beestonii'' have been found in rocks dating to the latest
Permian
The Permian ( ) is a geologic period and stratigraphic system which spans 47 million years from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.9 Mya. It is the last period of the Paleoz ...
. Quillworts are considered to be the closest extant relatives of the
fossil
A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...
tree ''
Lepidodendron
''Lepidodendron'' is an extinct genus of primitive vascular plants belonging to the family Lepidodendraceae, part of a group of Lycopodiopsida known as scale trees or arborescent lycophytes, related to Isoetes, quillworts and Lycopodiopsida, lyco ...
'', with which they share some unusual features including the development of both wood and bark, a modified shoot system acting as roots, bipolar growth, and an upright stance. Studies indicates that the Isoetes crown group which exist today evolved from a single lineage in the early
Cenozoic
The Cenozoic ( ; ) is Earth's current geological era, representing the last 66million years of Earth's history. It is characterised by the dominance of mammals, birds and flowering plants, a cooling and drying climate, and the current configura ...