''Selaginella'', also known as spikemosses or lesser clubmosses, is a genus of

lycophyte The lycophytes, when broadly circumscribed, are a group of vascular plants that include the clubmosses. They are sometimes placed in a division Lycopodiophyta or Lycophyta or in a subdivision Lycopodiophytina. They are one of the oldest lineag ...

. It is usually treated as the only genus in the family Selaginellaceae, with over 750 known species. This family is distinguished from

Lycopodiaceae The Lycopodiaceae (class Lycopodiopsida, order Lycopodiales) are an old family of vascular plants, including all of the core clubmosses and firmosses, comprising 17 accepted genera and about 500 known species. This family originated about 380 mi ...

(the clubmosses) by having scale-leaves bearing a ligule and by having spores of two types. They are sometimes included in an informal paraphyletic group called the "

fern allies Fern allies are a diverse group of seedless vascular plants that are not true ferns. Like ferns, a fern ally disperses by shedding spores to initiate an alternation of generations. Classification Originally, three or four groups of plants w ...

". The species '' S. moellendorffii'' is an important

model organism A model organism is a non-human species that is extensively studied to understand particular biological phenomena, with the expectation that discoveries made in the model organism will provide insight into the workings of other organisms. Mo ...

. Its genome has been sequenced by the

United States Department of Energy The United States Department of Energy (DOE) is an executive department of the U.S. federal government that oversees U.S. national energy policy and energy production, the research and development of nuclear power, the military's nuclear w ...

Joint Genome Institute The Joint Genome Institute (JGI) is a scientific user facility for integrative genomic science at Lawrence Berkeley National Laboratory. The mission of the JGI is to advance genomics research in support of the United States Department of Energy ...

. The name ''Selaginella'' was erected by Palisot de Beauvois solely for the species '' Selaginella selaginoides'', which turns out (with the closely related '' Selaginella deflexa'') to be a clade that is sister to all other ''Selaginellas'', so any definitive subdivision of the species into separate genera leaves two taxa in ''Selaginella'', with the hundreds of other species in new or resurrected genera. ''Selaginella'' occurs mostly in the tropical regions of the world, with a handful of species to be found in the arctic-alpine zones of both hemispheres. Fossils assignable to the modern genus are known spanning over 300 million years from the Late

Carboniferous The Carboniferous ( ) is a Geologic time scale, geologic period and System (stratigraphy), system of the Paleozoic era (geology), era that spans 60 million years, from the end of the Devonian Period Ma (million years ago) to the beginning of the ...

to the present.

Description

''Selaginella'' species are creeping or ascendant plants with simple, scale-like leaves ( microphylls) on branching stems from which roots also arise. The stems are aerial, horizontally creeping on the substratum (as in '' Selaginella kraussiana''), sub-erect (''

Selaginella trachyphylla ''Selaginella'', also known as spikemosses or lesser clubmosses, is a genus of lycophyte. It is usually treated as the only genus in the family Selaginellaceae, with over 750 known species. This family is distinguished from Lycopodiaceae (the ...

'') or erect (as in '' Selaginella erythropus''). The vascular steles are polystelic protosteles. Stem section shows the presence of more than two protosteles. Each stele is made up of diarch (having two strands of xylem) and

exarch An exarch (; from Ancient Greek ἔξαρχος ''exarchos'') was the holder of any of various historical offices, some of them being political or military and others being ecclesiastical. In the late Roman Empire and early Byzantine Empire, ...

(growing outward in)

xylem Xylem is one of the two types of transport tissue (biology), tissue in vascular plants, the other being phloem; both of these are part of the vascular bundle. The basic function of the xylem is to transport water upward from the roots to parts o ...

s. The steles are connected with the cortex by means of many tube-like structures called

trabeculae A trabecula (: trabeculae, from Latin for 'small beam') is a small, often microscopic, tissue element in the form of a small beam, strut or rod that supports or anchors a framework of parts within a body or organ. A trabecula generally has a ...

, which are modified endodermal cells with casparian strips on their lateral walls. The stems contain no pith. In ''Selaginella'', each microphyll and sporophyll has a small scale-like outgrowth called a

ligule A ligule (from "strap", variant of ''lingula'', from ''lingua'' "tongue") is a thin outgrowth at the junction of leaf A leaf (: leaves) is a principal appendage of the plant stem, stem of a vascular plant, usually borne laterally above g ...

at the base of the upper surface. The plants are heterosporous with spores of two different size classes, known as megaspores and microspores. In Selaginella rupestris fertilization takes place while the megaspore is still attached to the parent plant, and is only released after the embryo has produced

cotyledon A cotyledon ( ; ; "a cavity, small cup, any cup-shaped hollow", gen. (), ) is a "seed leaf" – a significant part of the embryo within the seed of a plant – and is formally defined as "the embryonic leaf in seed-bearing plants, one or mor ...

s and a root. Unusual for the lycopods, which nearly always have microphylls with a single unbranched vein, the microphylls of a few ''Selaginella'' species contain a branched vascular trace. Under dry conditions, some species of ''Selaginella'' can survive dehydration. In this state, they may roll up into brown balls and be uprooted, but can rehydrate under moist conditions, become green again and resume growth. This phenomenon is known as

poikilohydry Poikilohydry is the lack of ability (structural or functional mechanism) to maintain and/or regulate water content to achieve homeostasis of cells and tissue connected with quick equilibration of cell/tissue water content to that of the environment ...

, and poikilohydric plants such as ''Selaginella bryopteris'' are sometimes referred to as resurrection plants. There is no evidence of whole genome duplication in Selaginella's evolutionary history. Instead they have gone through tandem gene duplications, which is particularly noticeable in genes relevant for desiccation tolerance. Their chloroplasts are missing about two-thirds of their plastidial

tRNA Transfer ribonucleic acid (tRNA), formerly referred to as soluble ribonucleic acid (sRNA), is an adaptor molecule composed of RNA, typically 76 to 90 nucleotides in length (in eukaryotes). In a cell, it provides the physical link between the gene ...

genes, which are instead found in the genome of the

nucleus Nucleus (: nuclei) is a Latin word for the seed inside a fruit. It most often refers to: *Atomic nucleus, the very dense central region of an atom *Cell nucleus, a central organelle of a eukaryotic cell, containing most of the cell's DNA Nucleu ...

. The genus is unique among vascular plants in having species with monoplastidic cells, single giant chloroplasts, located mostly in their dorsal epidermal cells, but also in the upper mesophyll of some species. This appears to be a derived traits and an adaptation to low-light conditions, having originated at least twice. Cells with multiplastidic chloroplasts, more than ten chloroplasts per cell, are considered most basal, and are found in species exposed to more light. Oligoplastidic cells, cells with 3 to ten chloroplasts, are more adated to weaker light, and the monoplastidic species being the most shade-loving forms. It is estimated that 70% of Selaginella species are monoplastidic. These receive just 0.4~2.1% of full sunlight, while species with multiple chloroplasts live in open places where they on average receive more than 40.5% of full sunlight.

Taxonomy

Some scientists still place the Selaginellales in the class

Lycopodiopsida Lycopodiopsida is a class of vascular plants also known as lycopsids, lycopods, or lycophytes. Members of the class are also called clubmosses, firmosses, spikemosses and quillworts. They have dichotomously branching stems bearing simple leaves ...

(often misconstructed as "Lycopsida"). Some modern authors recognize three generic divisions of ''Selaginella'': ''Selaginella'', ''Bryodesma'' Sojak 1992, and ''Lycopodioides'' Boehm 1760. ''Lycopodioides'' would include the North American species ''S. apoda'' and ''S. eclipes'', while ''Bryodesma'' would include ''S. rupestris'' (as ''Bryodesma rupestre''). ''Stachygynandrum'' is also sometimes used to include the bulk of species. The first major attempt to define and subdivide the group was by

Palisot de Beauvois Ambroise Marie François Joseph Palisot, Baron de Beauvois (27 July 1752, in Arras – 21 January 1820, in Paris) was a French naturalist and zoologist. Palisot collected insects in Oware, Benin, Saint Domingue, and the United States, from 17 ...

in 1803–1805. He established the genus ''Selaginella'' as a monotypic genus, and placed the bulk of species in ''Stachygynandrum''. ''Gymnogynum'' was another monotypic genus, but that name is superseded by his own earlier name of ''Didiclis''. This turns out, today, to be a group of around 45–50 species also known as the ''Articulatae'', since his genus ''Didiclis/Gymnogynum'' was based on '' Selaginella plumosa''. He also described the genus ''Diplostachyum'' to include a group of species similar to ''Selaginella apoda''. Spring inflated the genus ''Selaginella'' to hold all selaginelloid species four decades later. Phylogenetic studies by Korall & KenrickKorall & Kenrick (2004): The phylogenetic history of Selaginellaceae based on DNA sequences from the plastid and nucleus: extreme substitution rates and rate heterogeneity. ''Molecular Phylogenetics and Evolution'', Volume 31, Issue 3, June 2004, Pages 852–864 determined that the ''Euselaginella'' group, comprising solely the type species, '' Selaginella selaginoides'' and a closely related Hawaiian species, '' Selaginella deflexa'', is a basal and anciently diverging sister to all other ''Selaginella'' species. Beyond this, their study split the remainder of species into two broad groups, one including the '' Bryodesma'' species, the '' Articulatae'', section '' Ericetorum'' Jermy and others, and the other centered on the broad ''Stachygynandrum'' group. In 2023, Zhou & Zhang suggested that the genus should be broken up into 19 different genera.

Zhang & Zhou, 2015 classification

* subgenus: ''Selaginella'' Type: ''S. selaginoides'' (L.) P.Beauv. ex Mart. & Schrank * subgenus: ''Boreoselaginella'' Type: ''S. sanguinolenta'' (L.) Spring * subgenus: ''Ericetorum'' Type: ''S. uliginosa'' (Labill.) Spring ** section: ''Lyallia'' Type: ''S. uliginosa'' (Labill.) Spring ** section: ''Myosurus'' Type: ''S. myosurus'' Alston ** section: ''Megalosporarum'' Type: ''S. exaltata'' (Kunze) Spring ** section: ''Articulatae'' Type: ''S. kraussiana'' (Kunze) A.Braun ** section: ''Homoeophyllae'' Type: ''S. rupestris'' (L.) Spring (=''Bryodesma'' Sojak or ''Tetragonostachys'' Jermy) ** section: ''Lepidophyllae'' Type: ''S. lepidophylla'' (Hook. & Grev.) Spring * subgenus: ''Pulviniella'' Type: ''S. pulvinata'' (Hook. & Grev.) Maxim * subgenus: ''Heterostachys'' Type: ''S. heterostachys'' Baker ** section: ''Oligomacrosporangiatae'' Type: ''Selaginella uncinata'' (Desv. ex Poir.) Spring ** section: ''Auriculatae'' Type: ''S. douglasii'' (Hook. & Grev.) Spring ** section: ''Homostachys'' Type: : ''S. helvetica'' (L.) Link ** section: ''Tetragonostachyae'' Type: ''S. proniflora'' (L.) Baker ** section: ''Heterostachys'' Type: ''S. brachystachya'' (Hook. & Grev.) Spring * subgenus: ''Stachygynandrum'' Type: ''S. flabellata'' (L.) Spring ** section: ''Plagiophyllae'' Type: ''S. biformis'' A.Braun ex Kuhn ** section: ''Circinatae'' Type: ''S. involvens'' (Sw.) Spring ** section: ''Heterophyllae'' Type: ''S. flexuosa'' Spring ** section: ''Austroamericanae'' Type: ''S. hartwegiana'' Spring ** section: ''Pallescentes'' Type: ''S. pallescens'' (C.Presl) Spring ** section: ''Proceres'' Type: ''S. oaxacana'' Spring ** section: ''Ascendentes'' Type: ''S. alopecuroides'' Baker

Species

There are about 750 known species of ''Selaginella''. They show a wide range of characters; the genus is overdue for a revision which might include subdivision into several genera. Species of spikemoss include: * ''

Selaginella apoda ''Selaginella apoda'', commonly known as meadow spikemoss, is a perennial lycophyte native to much of the eastern United States and parts of northeastern Mexico. The life cycle is the shortest of the genus ''Selaginella'', as well as one of the s ...

'' – meadow spikemoss; eastern

North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...

* '' Selaginella arizonica'' Maxon – west Texas to Arizona and Sonora, Mexico * '' Selaginella asprella'' * '' Selaginella bifida'' – Rodrigues Island * '' Selaginella biformis'' * '' Selaginella bigelovii'' * '' Selaginella braunii'' – Braun's spikemoss;

China China, officially the People's Republic of China (PRC), is a country in East Asia. With population of China, a population exceeding 1.4 billion, it is the list of countries by population (United Nations), second-most populous country after ...

* '' Selaginella bryopteris'' – sanjeevani;

India India, officially the Republic of India, is a country in South Asia. It is the List of countries and dependencies by area, seventh-largest country by area; the List of countries by population (United Nations), most populous country since ...

* '' Selaginella canaliculata'' – clubmoss;

southeast Asia Southeast Asia is the geographical United Nations geoscheme for Asia#South-eastern Asia, southeastern region of Asia, consisting of the regions that are situated south of China, east of the Indian subcontinent, and northwest of the Mainland Au ...

Maluku Islands The Maluku Islands ( ; , ) or the Moluccas ( ; ) are an archipelago in the eastern part of Indonesia. Tectonics, Tectonically they are located on the Halmahera Plate within the Molucca Sea Collision Zone. Geographically they are located in West ...

* '' Selaginella carinata'' * '' Selaginella cinerascens'' * '' Selaginella densa'' – lesser spikemoss; western North America * '' Selaginella denticulata'' * '' Selaginella eclipes'' – hidden spikemoss; eastern North America * '' Selaginella elmeri'' * '' Selaginella eremophila'' Maxon * '' Selaginella erythropus'' * '' Selaginella galotteii'' * '' Selaginella gigantea'' – From Venezuela. * '' Selaginella hansenii'' * '' Selaginella kraussiana'' – Krauss's spikemoss;

Africa Africa is the world's second-largest and second-most populous continent after Asia. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 20% of Earth's land area and 6% of its total surfac ...

Azores The Azores ( , , ; , ), officially the Autonomous Region of the Azores (), is one of the two autonomous regions of Portugal (along with Madeira). It is an archipelago composed of nine volcanic islands in the Macaronesia region of the North Atl ...

* '' Selaginella lepidophylla'' – resurrection plant, dinosaur plant, and flower of stone; Chihuahuan Desert,

* '' Selaginella martensii'' – variegated spikemoss * '' Selaginella moellendorffii'' * '' Selaginella oregana'' * ''

Selaginella plana ''Selaginella plana'', commonly known as the Asian spikemoss, is a lycophyte native to tropical Asia. Distribution ''Selaginella plana'' occurs in tropical regions of Asia, including India, Indochina, and the Malay Archipelago. Native populatio ...

'' – Asian spikemoss; tropical

Asia Asia ( , ) is the largest continent in the world by both land area and population. It covers an area of more than 44 million square kilometres, about 30% of Earth's total land area and 8% of Earth's total surface area. The continent, which ...

* '' Selaginella poulteri'' * '' Selaginella pulcherrima'' * '' Selaginella rupestris'' – rock spikemoss, festoon pine, and northern Selaginella (eastern North America) * '' Selaginella rupincola'' Underw. – west Texas to Arizona and Sonora, Mexico * '' Selaginella selaginoides'' – lesser clubmoss; north temperate

Europe Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and Asia to the east ...

and

) * '' Selaginella sericea'' A.Braun –

Ecuador Ecuador, officially the Republic of Ecuador, is a country in northwestern South America, bordered by Colombia on the north, Peru on the east and south, and the Pacific Ocean on the west. It also includes the Galápagos Province which contain ...

* '' Selaginella serpens'' * '' Selaginella sibirica'' * '' Selaginella stellata'' – starry spikemoss; Mexico,

Central America Central America is a subregion of North America. Its political boundaries are defined as bordering Mexico to the north, Colombia to the southeast, the Caribbean to the east, and the Pacific Ocean to the southwest. Central America is usually ...

* '' Selaginella substipitata'' * '' Selaginella tamariscina'' * '' Selaginella tortipila'' * '' Selaginella uliginosa'' –

Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...

* '' Selaginella umbrosa'' * '' Selaginella uncinata'' – peacock moss, peacock spikemoss, blue spikemoss * '' Selaginella underwoodii'' Hieron. – west Texas to Wyoming and west into Arizona * '' Selaginella wallacei'' * '' Selaginella watsonii'' * '' Selaginella willdenowii'' – Willdenow's spikemoss, peacock fern; southeast Asia A few species of ''Selaginella'' are

desert A desert is a landscape where little precipitation occurs and, consequently, living conditions create unique biomes and ecosystems. The lack of vegetation exposes the unprotected surface of the ground to denudation. About one-third of the la ...

plants known as "resurrection plants", because they curl up in a tight, brown or reddish ball during dry times, and uncurl and turn green in the presence of moisture. Other species are tropical

forest A forest is an ecosystem characterized by a dense ecological community, community of trees. Hundreds of definitions of forest are used throughout the world, incorporating factors such as tree density, tree height, land use, legal standing, ...

plants that appear at first glance to be

fern The ferns (Polypodiopsida or Polypodiophyta) are a group of vascular plants (plants with xylem and phloem) that reproduce via spores and have neither seeds nor flowers. They differ from mosses by being vascular, i.e., having specialized tissue ...

Cultivation

A number of ''Selaginella'' species are popular plants for cultivation, mostly tropical species. Some of the species popularly cultivated and actively available commercially include: * ''S. kraussiana'': golden clubmoss * ''S. martensii'': frosty fern * ''S. moellendorffii'': gemmiferous spikemoss * ''S. erythropus'': red selaginella or ruby-red spikemoss * ''S. uncinata'': peacock moss * ''S. lepidophylla'': resurrection plant * ''S. braunii'': arborvitae fern

References

External links

* * {{Authority control Lycophyte genera