Parnassiaceae
Encyclopedia
Parnassiaceae Gray
is a family
of Flowering plant
s in the eudicot order
Celastrales
. It is not recognized in the APG III system
of plant classification
. When that system
was published in 2009, Parnassiaceae was treated as a segregate
of an expanded Celastraceae
.
Parnassiaceae has only two genera
, Lepuropetalon
and Parnassia. Lepuropetalon has only one species
, Lepuropetalon spathulatum, a winter annual that usually prefers sand
y soil
. It is one of the smallest of flowering plants, up to 2cm tall. Lepuropetalon has a disjunct distribution
, being known from the southeastern US and central Chile
, but is probably far more common than has been reported.
Parnassia is a genus of perennial herbs
, up to 60cm tall, that grow in bog
s, marsh
es, and other wet areas, mostly in cool to cold climate
s of the north temperate zone. There are at least 70 species. Sixty-three species occur in China
and 49 of these occur nowhere else. A second area of diversity
for Parnassia is North America
and about 9 species occur there. Parnassia palustris
is the most well known and widely distributed species. It ranges through most of northern Eurasia
, Canada
, and the western United States
. Parnassia palustris is widely cultivated
. About 10 species are known in cultivation, all as ornamentals
.
(Parnassia) or winter annuals without a rhizome (Lepuropetalon). The youngest part of the stem has three collateral vascular bundle
s. On the stems, leaves, and flowers, the epidermis
has sacs filled with tannin
. The leaves are alternate or subopposite, without stipule
s, and the margins are entire
. The leaf blade is wide compared to its length and the secondary venation is subpalmate.
In Parnassia, the leaves are crowded into a basal rosette
with a few cauline leaves above. The leaves are all cauline in Lepuropetalon.
In both genera, the lower cauline leaves are pseudosessile
, which means that the petioles
are adnate to the stems. The upper cauline leaves, if present, are truly sessile
.
The inflorescence
consists of one, or rarely two, flowers that face upward and are at the end of a peduncle
that has few or no leaves. The flower
s are perfect and slightly zygomorphic. The five sepal
s are shortly connate at their bases, and persistent through maturity of the fruit. The petal
s are either absent, or five and free from each other. In Parnassia, the petals are showy and white or cream, with conspicuous veins that are usually green or gray. The margins are entire
, toothed, or fimbriate. In Lepuropetalon, the petals are rudimentary or absent.
In both genera, the five stamen
s are free from each other. They are placed opposite the sepals and therefore alternate with the petals. The anthers open in sequence above the gynoecium
(see next section). The five staminode
s are free and placed opposite the petals. They mature after the stamens. Each consists of a nectariferous pad with filamentous rays arising from its edge. Each ray is terminated by a large globular gland.
The ovary
is superior or half inferior and consists of 3 or 4, rarely 5, fused carpels. The walls of the carpels are incomplete so that the ovary is unilocular
in its upper part. The placentation
is parietal
. The ovule
s are attached to T-shaped placentas
in Parnassia, and directly to the ovary wall in Lepuropetalon. The style is absent or very short. The stigmas
are decurrent
along the commissure
s of the ovary and sometimes extended above, to form false styles called stylodia. The stigmatic areas are dry. The megagametophyte is of the Polygonum type.
The fruit
is an erect, membranous capsule
, which opens at the apex only. The seed
s are small, light, and numerous.
s. But for one who examines these plants more closely, further oddities will come to light.
The lowest leaves on the stem appear to be sessile
, but in fact, the petiole
is adnate to the stem and embedded in it. The conductive vessels
that enervate the leaf depart from those of the stem far below where the leaf is attached.
As soon as the flower opens, the stamens begin to elongate. One of them bends inward, opens the theca
e of its anther, and dumps its pollen
on the ovary
. It then bends away from the ovary to the outside of the flower. Another stamen then repeats this process. It takes about one day for a stamen to complete its motions, and the order in which they do so varies from one flower to another.
The area that is receptive to pollen, the stigmatic area
, is not confined to the apex of the ovary or mounted on a style as in most flowers, but extends in bands down the sides of the ovary along the commissure
s, the seams where the carpels that compose the ovary are joined together. Such commissural stigmas have been discovered in Celastraceae
, but as late as 1972, they were known only from Parnassiaceae and from the basal eudicot family Papaveraceae
.
Lepuropetalon shares with Parnassia the pseudosessile leaves and the commissural stigmas. It also dumps its pollen on the ovary, but without the elaborate dance of the stamens. Unlike Parnassia, however, its staminodes are small and lack glands.
in Greece
. In 1821, Samuel Frederick Gray
put Parnassia in its own family, Parnassiaceae. In that same year, Stephen Elliott
gave Lepuropetalon its name and published a description of it. The name is from two Greek
words, lepyron, "husk, rind, or shell", and petalon, "leaf or petal".
In 1930, Adolf Engler
published descriptions of Lepuropetalon and Parnassia with detailed illustrations. He did not consider them to be closely related and placed each in its own subfamily among the 15 subfamilies that he recognized in Saxifragaceae
. Others thought that they were closely related. One of these was Steven Spongberg, who did a detailed study of Lepuropetalon and placed it in Saxifragaceae in the same subfamily with Parnassia. Most authors have followed Engler or Spongberg in their treatment of these two genera, but often with considerable doubt. Several other possible relationships have been proposed.
In 2001, a DNA
study showed that Lepuropetalon and Parnassia were much closer to each other than to any others. This was the first DNA study to give strong statistical support (98% bootstrap
support) for this relationship.
In 2005, a study of flower structure concluded that the family Parnassiaceae belonged in the order Celastrales
with Lepidobotryaceae
, and a broadly defined Celastraceae
, including Mortonia
and Pottingeria
.
In 2006, a study of DNA sequence
s confirmed that Lepuropetalon and Parnassia form a strongly supported
clade
. This study also showed strong support
for a pentatomy
consisting of Pottingeria
, Mortonia
, Parnassiaceae, and two clades of genera
from Celastraceae
as that family had been circumscribed
in APG II. The relationships between these five clades remain unresolved.
In 2009, the Angiosperm Phylogeny Group
expanded the family Celastraceae to consist of the five clades of the pentatomy mentioned above. A phylogenetic infrafamilial
classification
of Celastraceae sensu
APG III has not yet been published.
Samuel Frederick Gray
Samuel Frederick Gray was a British botanist, mycologist, and pharmacologist. He was the father of the zoologists John Edward Gray and George Robert Gray.-Background:...
is a family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
of Flowering plant
Flowering plant
The flowering plants , also known as Angiospermae or Magnoliophyta, are the most diverse group of land plants. Angiosperms are seed-producing plants like the gymnosperms and can be distinguished from the gymnosperms by a series of synapomorphies...
s in the eudicot order
Order (biology)
In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...
Celastrales
Celastrales
Celastrales is an order of flowering plants. They are found throughout the tropics and subtropics, with only a few species extending far into the temperate regions. There are about 1200 to 1350 species in about 100 genera. All but 7 of these genera are in the large family Celastraceae...
. It is not recognized in the APG III system
APG III system
The APG III system of flowering plant classification is the third version of a modern, mostly molecular-based, system of plant taxonomy...
of plant classification
History of plant systematics
The history of plant systematics—the biological classification of plants—stretches from the work of ancient Greek to modern evolutionary biologists. As a field of science, plant systematics came into being only slowly, early plant lore usually being treated as part of the study of...
. When that system
Plant taxonomy
Plant taxonomy is the science that finds, describes, classifies, identifies, and names plants. It thus is one of the main branches of taxonomy.Plant taxonomy is closely allied to plant systematics, and there is no sharp boundary between the two...
was published in 2009, Parnassiaceae was treated as a segregate
Segregate (taxonomy)
In taxonomy, a segregate, or a segregate taxon is created when a taxon is split off, from another taxon. This other taxon will be better known, usually bigger, and will continue to exist, even after the segregate taxon has been split off...
of an expanded Celastraceae
Celastraceae
The Celastraceae , is a family of about 90-100 genera and 1,300 species of vines, shrubs and small trees, belonging to the order Celastrales...
.
Parnassiaceae has only two genera
Genera
Genera is a commercial operating system and development environment for Lisp machines developed by Symbolics. It is essentially a fork of an earlier operating system originating on the MIT AI Lab's Lisp machines which Symbolics had used in common with LMI and Texas Instruments...
, Lepuropetalon
Lepuropetalon
Lepuropetalon is a genus of flowering plants in the family Celastraceae as that family was defined by the Angiosperm Phylogeny Group in 2009. Before the publication of the APG III system in 2009, Lepuropetalon had been placed with Parnassia in the family Parnassiaceae, now usually treated as a...
and Parnassia. Lepuropetalon has only one species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
, Lepuropetalon spathulatum, a winter annual that usually prefers sand
Sand
Sand is a naturally occurring granular material composed of finely divided rock and mineral particles.The composition of sand is highly variable, depending on the local rock sources and conditions, but the most common constituent of sand in inland continental settings and non-tropical coastal...
y soil
Soil
Soil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics...
. It is one of the smallest of flowering plants, up to 2cm tall. Lepuropetalon has a disjunct distribution
Disjunct distribution
In biology, a taxon with a disjunct distribution is one that has two or more groups that are related but widely separated from each other geographically...
, being known from the southeastern US and central Chile
Chile
Chile ,officially the Republic of Chile , is a country in South America occupying a long, narrow coastal strip between the Andes mountains to the east and the Pacific Ocean to the west. It borders Peru to the north, Bolivia to the northeast, Argentina to the east, and the Drake Passage in the far...
, but is probably far more common than has been reported.
Parnassia is a genus of perennial herbs
Herbaceous plant
A herbaceous plant is a plant that has leaves and stems that die down at the end of the growing season to the soil level. They have no persistent woody stem above ground...
, up to 60cm tall, that grow in bog
Bog
A bog, quagmire or mire is a wetland that accumulates acidic peat, a deposit of dead plant material—often mosses or, in Arctic climates, lichens....
s, marsh
Marsh
In geography, a marsh, or morass, is a type of wetland that is subject to frequent or continuous flood. Typically the water is shallow and features grasses, rushes, reeds, typhas, sedges, other herbaceous plants, and moss....
es, and other wet areas, mostly in cool to cold climate
Climate
Climate encompasses the statistics of temperature, humidity, atmospheric pressure, wind, rainfall, atmospheric particle count and other meteorological elemental measurements in a given region over long periods...
s of the north temperate zone. There are at least 70 species. Sixty-three species occur in China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
and 49 of these occur nowhere else. A second area of diversity
Biodiversity
Biodiversity is the degree of variation of life forms within a given ecosystem, biome, or an entire planet. Biodiversity is a measure of the health of ecosystems. Biodiversity is in part a function of climate. In terrestrial habitats, tropical regions are typically rich whereas polar regions...
for Parnassia is North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
and about 9 species occur there. Parnassia palustris
Parnassia palustris
Parnassia palustris, commonly called Marsh Grass-of-Parnassus, Northern Grass-of-Parnassus, and Bog-star, is a species of the genus Parnassia....
is the most well known and widely distributed species. It ranges through most of northern Eurasia
Eurasia
Eurasia is a continent or supercontinent comprising the traditional continents of Europe and Asia ; covering about 52,990,000 km2 or about 10.6% of the Earth's surface located primarily in the eastern and northern hemispheres...
, Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
, and the western United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
. Parnassia palustris is widely cultivated
Gardening
Gardening is the practice of growing and cultivating plants. Ornamental plants are normally grown for their flowers, foliage, or overall appearance; useful plants are grown for consumption , for their dyes, or for medicinal or cosmetic use...
. About 10 species are known in cultivation, all as ornamentals
Ornamental plant
Ornamental plants are plants that are grown for decorative purposes in gardens and landscape design projects, as house plants, for cut flowers and specimen display...
.
Description
The Parnassiaceae are rhizomatous perennial herbsHerbaceous plant
A herbaceous plant is a plant that has leaves and stems that die down at the end of the growing season to the soil level. They have no persistent woody stem above ground...
(Parnassia) or winter annuals without a rhizome (Lepuropetalon). The youngest part of the stem has three collateral vascular bundle
Vascular bundle
A vascular bundle is a part of the transport system in vascular plants. The transport itself happens in vascular tissue, which exists in two forms: xylem and phloem. Both these tissues are present in a vascular bundle, which in addition will include supporting and protective tissues...
s. On the stems, leaves, and flowers, the epidermis
Epidermis (botany)
The epidermis is a single-layered group of cells that covers plants' leaves, flowers, roots and stems. It forms a boundary between the plant and the external environment. The epidermis serves several functions, it protects against water loss, regulates gas exchange, secretes metabolic compounds,...
has sacs filled with tannin
Tannin
A tannin is an astringent, bitter plant polyphenolic compound that binds to and precipitates proteins and various other organic compounds including amino acids and alkaloids.The term tannin refers to the use of...
. The leaves are alternate or subopposite, without stipule
Stipule
In botany, stipule is a term coined by Linnaeus which refers to outgrowths borne on either side of the base of a leafstalk...
s, and the margins are entire
Leaf shape
In botany, leaf shape is characterised with the following terms :* Acicular : Slender and pointed, needle-like* Acuminate : Tapering to a long point...
. The leaf blade is wide compared to its length and the secondary venation is subpalmate.
In Parnassia, the leaves are crowded into a basal rosette
Rosette (botany)
In botany, a rosette is a circular arrangement of leaves, with all the leaves at a single height.Though rosettes usually sit near the soil, their structure is an example of a modified stem.-Function:...
with a few cauline leaves above. The leaves are all cauline in Lepuropetalon.
In both genera, the lower cauline leaves are pseudosessile
Petiole (botany)
In botany, the petiole is the stalk attaching the leaf blade to the stem. The petiole usually has the same internal structure as the stem. Outgrowths appearing on each side of the petiole are called stipules. Leaves lacking a petiole are called sessile, or clasping when they partly surround the...
, which means that the petioles
Petiole (botany)
In botany, the petiole is the stalk attaching the leaf blade to the stem. The petiole usually has the same internal structure as the stem. Outgrowths appearing on each side of the petiole are called stipules. Leaves lacking a petiole are called sessile, or clasping when they partly surround the...
are adnate to the stems. The upper cauline leaves, if present, are truly sessile
Sessility (botany)
In botany, sessility is a characteristic of plants whose flowers or leaves are borne directly from the stem or peduncle, and thus lack a petiole or pedicel...
.
The inflorescence
Inflorescence
An inflorescence is a group or cluster of flowers arranged on a stem that is composed of a main branch or a complicated arrangement of branches. Strictly, it is the part of the shoot of seed plants where flowers are formed and which is accordingly modified...
consists of one, or rarely two, flowers that face upward and are at the end of a peduncle
Peduncle (botany)
In botany, a peduncle is a stem supporting an inflorescence, or after fecundation, an infructescence.The peduncle is a stem, usually green and without leaves, though sometimes colored or supporting small leaves...
that has few or no leaves. The flower
Flower
A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants . The biological function of a flower is to effect reproduction, usually by providing a mechanism for the union of sperm with eggs...
s are perfect and slightly zygomorphic. The five sepal
Sepal
A sepal is a part of the flower of angiosperms . Collectively the sepals form the calyx, which is the outermost whorl of parts that form a flower. Usually green, sepals have the typical function of protecting the petals when the flower is in bud...
s are shortly connate at their bases, and persistent through maturity of the fruit. The petal
Petal
Petals are modified leaves that surround the reproductive parts of flowers. They often are brightly colored or unusually shaped to attract pollinators. Together, all of the petals of a flower are called a corolla. Petals are usually accompanied by another set of special leaves called sepals lying...
s are either absent, or five and free from each other. In Parnassia, the petals are showy and white or cream, with conspicuous veins that are usually green or gray. The margins are entire
Leaf shape
In botany, leaf shape is characterised with the following terms :* Acicular : Slender and pointed, needle-like* Acuminate : Tapering to a long point...
, toothed, or fimbriate. In Lepuropetalon, the petals are rudimentary or absent.
In both genera, the five stamen
Stamen
The stamen is the pollen producing reproductive organ of a flower...
s are free from each other. They are placed opposite the sepals and therefore alternate with the petals. The anthers open in sequence above the gynoecium
Gynoecium
Gynoecium is most commonly used as a collective term for all carpels in a flower. A carpel is the ovule and seed producing reproductive organ in flowering plants. Carpels are derived from ovule-bearing leaves which evolved to form a closed structure containing the ovules...
(see next section). The five staminode
Staminode
In botany, a staminode is an often rudimentary, sterile or abortive stamen. This means that it does not produce pollen. Staminodes are frequently inconspicuous and stamen-like, usually occurring at the inner whorl of the flower, but are also sometimes long enough to protrude from the...
s are free and placed opposite the petals. They mature after the stamens. Each consists of a nectariferous pad with filamentous rays arising from its edge. Each ray is terminated by a large globular gland.
The ovary
Ovary (plants)
In the flowering plants, an ovary is a part of the female reproductive organ of the flower or gynoecium. Specifically, it is the part of the pistil which holds the ovule and is located above or below or at the point of connection with the base of the petals and sepals...
is superior or half inferior and consists of 3 or 4, rarely 5, fused carpels. The walls of the carpels are incomplete so that the ovary is unilocular
Locule
A locule is a small cavity or compartment within an organ or part of an organism ....
in its upper part. The placentation
Placentation
In biology, placentation refers to the formation, type and structure, or arrangement of placentas. The function of placentation is to transfer nutrients from maternal tissue to a growing embryo...
is parietal
Placentation
In biology, placentation refers to the formation, type and structure, or arrangement of placentas. The function of placentation is to transfer nutrients from maternal tissue to a growing embryo...
. The ovule
Ovule
Ovule means "small egg". In seed plants, the ovule is the structure that gives rise to and contains the female reproductive cells. It consists of three parts: The integument forming its outer layer, the nucellus , and the megaspore-derived female gametophyte in its center...
s are attached to T-shaped placentas
Placentation
In biology, placentation refers to the formation, type and structure, or arrangement of placentas. The function of placentation is to transfer nutrients from maternal tissue to a growing embryo...
in Parnassia, and directly to the ovary wall in Lepuropetalon. The style is absent or very short. The stigmas
Stigma (botany)
The stigma is the receptive tip of a carpel, or of several fused carpels, in the gynoecium of a flower. The stigma receives pollen at pollination and it is on the stigma that the pollen grain germinates. The stigma is adapted to catch and trap pollen with various hairs, flaps, or sculpturings...
are decurrent
Decurrent
Decurrent is a term used in botany and mycology to describe plant or fungal parts that extend downward.In botany, the term is most often applied to leaf blades that partly wrap or have wings around the stem or petiole and extend down along the stem...
along the commissure
Commissure
A commissure is the place where two things are joined. The term is used especially in the fields of anatomy and biology.In anatomy, commissure refers to a bundle of nerve fibers that cross the midline at their level of origin or entry .* The most common usage of the term refers to the brain's...
s of the ovary and sometimes extended above, to form false styles called stylodia. The stigmatic areas are dry. The megagametophyte is of the Polygonum type.
The fruit
Fruit
In broad terms, a fruit is a structure of a plant that contains its seeds.The term has different meanings dependent on context. In non-technical usage, such as food preparation, fruit normally means the fleshy seed-associated structures of certain plants that are sweet and edible in the raw state,...
is an erect, membranous capsule
Capsule (fruit)
In botany a capsule is a type of simple, dry fruit produced by many species of flowering plants. A capsule is a structure composed of two or more carpels that in most cases is dehiscent, i.e. at maturity, it splits apart to release the seeds within. A few capsules are indehiscent, for example...
, which opens at the apex only. The seed
Seed
A seed is a small embryonic plant enclosed in a covering called the seed coat, usually with some stored food. It is the product of the ripened ovule of gymnosperm and angiosperm plants which occurs after fertilization and some growth within the mother plant...
s are small, light, and numerous.
Oddities
Parnassias are often grown as curiosities for their unique and prominent staminodeStaminode
In botany, a staminode is an often rudimentary, sterile or abortive stamen. This means that it does not produce pollen. Staminodes are frequently inconspicuous and stamen-like, usually occurring at the inner whorl of the flower, but are also sometimes long enough to protrude from the...
s. But for one who examines these plants more closely, further oddities will come to light.
The lowest leaves on the stem appear to be sessile
Sessility (botany)
In botany, sessility is a characteristic of plants whose flowers or leaves are borne directly from the stem or peduncle, and thus lack a petiole or pedicel...
, but in fact, the petiole
Petiole (botany)
In botany, the petiole is the stalk attaching the leaf blade to the stem. The petiole usually has the same internal structure as the stem. Outgrowths appearing on each side of the petiole are called stipules. Leaves lacking a petiole are called sessile, or clasping when they partly surround the...
is adnate to the stem and embedded in it. The conductive vessels
Vascular bundle
A vascular bundle is a part of the transport system in vascular plants. The transport itself happens in vascular tissue, which exists in two forms: xylem and phloem. Both these tissues are present in a vascular bundle, which in addition will include supporting and protective tissues...
that enervate the leaf depart from those of the stem far below where the leaf is attached.
As soon as the flower opens, the stamens begin to elongate. One of them bends inward, opens the theca
Theca
A theca refers to any case, covering, or sheath.In botany, the theca of an angiosperm consists a pair of microsporangia that are adjacent to each other and share a common area of dehiscence called the stomium. Any part of a microsporophyll that bears microsporangia is called an anther. Most...
e of its anther, and dumps its pollen
Pollen
Pollen is a fine to coarse powder containing the microgametophytes of seed plants, which produce the male gametes . Pollen grains have a hard coat that protects the sperm cells during the process of their movement from the stamens to the pistil of flowering plants or from the male cone to the...
on the ovary
Ovary (plants)
In the flowering plants, an ovary is a part of the female reproductive organ of the flower or gynoecium. Specifically, it is the part of the pistil which holds the ovule and is located above or below or at the point of connection with the base of the petals and sepals...
. It then bends away from the ovary to the outside of the flower. Another stamen then repeats this process. It takes about one day for a stamen to complete its motions, and the order in which they do so varies from one flower to another.
The area that is receptive to pollen, the stigmatic area
Stigma (botany)
The stigma is the receptive tip of a carpel, or of several fused carpels, in the gynoecium of a flower. The stigma receives pollen at pollination and it is on the stigma that the pollen grain germinates. The stigma is adapted to catch and trap pollen with various hairs, flaps, or sculpturings...
, is not confined to the apex of the ovary or mounted on a style as in most flowers, but extends in bands down the sides of the ovary along the commissure
Commissure
A commissure is the place where two things are joined. The term is used especially in the fields of anatomy and biology.In anatomy, commissure refers to a bundle of nerve fibers that cross the midline at their level of origin or entry .* The most common usage of the term refers to the brain's...
s, the seams where the carpels that compose the ovary are joined together. Such commissural stigmas have been discovered in Celastraceae
Celastraceae
The Celastraceae , is a family of about 90-100 genera and 1,300 species of vines, shrubs and small trees, belonging to the order Celastrales...
, but as late as 1972, they were known only from Parnassiaceae and from the basal eudicot family Papaveraceae
Papaveraceae
Papaveraceae, informally known as the poppy family, are an economically important family of 44 genera and approximately 770 species of flowering plants in the order Ranunculales. The family is cosmopolitan, occurring in temperate and subtropical climates, but almost unknown in the tropics...
.
Lepuropetalon shares with Parnassia the pseudosessile leaves and the commissural stigmas. It also dumps its pollen on the ovary, but without the elaborate dance of the stamens. Unlike Parnassia, however, its staminodes are small and lack glands.
Relationships
The genus Parnassia was named by Linnaeus in 1753 for Mount ParnassusMount Parnassus
Mount Parnassus, also Parnassos , is a mountain of limestone in central Greece that towers above Delphi, north of the Gulf of Corinth, and offers scenic views of the surrounding olive groves and countryside. According to Greek mythology, this mountain was sacred to Apollo and the Corycian nymphs,...
in Greece
Greece
Greece , officially the Hellenic Republic , and historically Hellas or the Republic of Greece in English, is a country in southeastern Europe....
. In 1821, Samuel Frederick Gray
Samuel Frederick Gray
Samuel Frederick Gray was a British botanist, mycologist, and pharmacologist. He was the father of the zoologists John Edward Gray and George Robert Gray.-Background:...
put Parnassia in its own family, Parnassiaceae. In that same year, Stephen Elliott
Stephen Elliott (botanist)
Stephen Elliott was an American legislator, banker, educator, and botanist who is today remembered for having written one of the most important works in American botany, A Sketch of the Botany of South-Carolina and Georgia.-Biography:Stephen Elliott was born in Beaufort, South Carolina on...
gave Lepuropetalon its name and published a description of it. The name is from two Greek
Greek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...
words, lepyron, "husk, rind, or shell", and petalon, "leaf or petal".
In 1930, Adolf Engler
Adolf Engler
Heinrich Gustav Adolf Engler was a German botanist. He is notable for his work on plant taxonomy and phytogeography, like Die Natürlichen Pflanzenfamilien , edited with Karl A. E...
published descriptions of Lepuropetalon and Parnassia with detailed illustrations. He did not consider them to be closely related and placed each in its own subfamily among the 15 subfamilies that he recognized in Saxifragaceae
Saxifragaceae
Saxifragaceae is a plant family with about 460 known species in 36 genera. In Europe there are 12 genera.The flowers are hermaphroditic and actinomorphic...
. Others thought that they were closely related. One of these was Steven Spongberg, who did a detailed study of Lepuropetalon and placed it in Saxifragaceae in the same subfamily with Parnassia. Most authors have followed Engler or Spongberg in their treatment of these two genera, but often with considerable doubt. Several other possible relationships have been proposed.
In 2001, a DNA
DNA
Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...
study showed that Lepuropetalon and Parnassia were much closer to each other than to any others. This was the first DNA study to give strong statistical support (98% bootstrap
Bootstrapping (statistics)
In statistics, bootstrapping is a computer-based method for assigning measures of accuracy to sample estimates . This technique allows estimation of the sample distribution of almost any statistic using only very simple methods...
support) for this relationship.
In 2005, a study of flower structure concluded that the family Parnassiaceae belonged in the order Celastrales
Celastrales
Celastrales is an order of flowering plants. They are found throughout the tropics and subtropics, with only a few species extending far into the temperate regions. There are about 1200 to 1350 species in about 100 genera. All but 7 of these genera are in the large family Celastraceae...
with Lepidobotryaceae
Lepidobotryaceae
Lepidobotryaceae is a flowering plant family in the order Celastrales. It contains only two species, Lepidobotrys staudtii and Ruptiliocarpon caracolito.- Description :...
, and a broadly defined Celastraceae
Celastraceae
The Celastraceae , is a family of about 90-100 genera and 1,300 species of vines, shrubs and small trees, belonging to the order Celastrales...
, including Mortonia
Mortonia
Mortonia is a small genus of flowering shrubs known as saddlebushes or mortonias. These are rough, hairy shrubs with leathery leaves and panicles of fleshy white to purplish flowers. They bear nutlets containing 1 seed each...
and Pottingeria
Pottingeria
Pottingeria is a small tree or large shrub native to mountainous areas of southeast Asia .It had long been thought, at least by some, to belong in the order Celastrales. In a phylogenetic study of that order in 2006, Pottingeria was found to be a member of the order, but not of any of its families...
.
In 2006, a study of DNA sequence
DNA sequence
The sequence or primary structure of a nucleic acid is the composition of atoms that make up the nucleic acid and the chemical bonds that bond those atoms. Because nucleic acids, such as DNA and RNA, are unbranched polymers, this specification is equivalent to specifying the sequence of...
s confirmed that Lepuropetalon and Parnassia form a strongly supported
Resampling (statistics)
In statistics, resampling is any of a variety of methods for doing one of the following:# Estimating the precision of sample statistics by using subsets of available data or drawing randomly with replacement from a set of data points # Exchanging labels on data points when performing significance...
clade
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
. This study also showed strong support
Bootstrapping (statistics)
In statistics, bootstrapping is a computer-based method for assigning measures of accuracy to sample estimates . This technique allows estimation of the sample distribution of almost any statistic using only very simple methods...
for a pentatomy
Polytomy
A polytomy , meaning many temporal based branches, is a section of a phylogeny in which the evolutionary relationships can not be fully resolved to dichotomies. In a phylogenetic tree, a polytomy is represented as a node which has more than two immediate descending branches...
consisting of Pottingeria
Pottingeria
Pottingeria is a small tree or large shrub native to mountainous areas of southeast Asia .It had long been thought, at least by some, to belong in the order Celastrales. In a phylogenetic study of that order in 2006, Pottingeria was found to be a member of the order, but not of any of its families...
, Mortonia
Mortonia
Mortonia is a small genus of flowering shrubs known as saddlebushes or mortonias. These are rough, hairy shrubs with leathery leaves and panicles of fleshy white to purplish flowers. They bear nutlets containing 1 seed each...
, Parnassiaceae, and two clades of genera
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
from Celastraceae
Celastraceae
The Celastraceae , is a family of about 90-100 genera and 1,300 species of vines, shrubs and small trees, belonging to the order Celastrales...
as that family had been circumscribed
Circumscription (taxonomy)
In taxonomy, circumscription is the definition of the limits of a taxonomic group of organisms. One goal of taxonomy is to achieve a stable circumscription for every taxonomic group. Achieving stability can be simple or difficult....
in APG II. The relationships between these five clades remain unresolved.
In 2009, the Angiosperm Phylogeny Group
Angiosperm Phylogeny Group
The Angiosperm Phylogeny Group, or APG, refers to an informal international group of systematic botanists who came together to try to establish a consensus on the taxonomy of flowering plants that would reflect new knowledge about plant relationships discovered through phylogenetic studies., three...
expanded the family Celastraceae to consist of the five clades of the pentatomy mentioned above. A phylogenetic infrafamilial
Taxonomic rank
In biological classification, rank is the level in a taxonomic hierarchy. Examples of taxonomic ranks are species, genus, family, and class. Each rank subsumes under it a number of less general categories...
classification
Biological classification
Biological classification, or scientific classification in biology, is a method to group and categorize organisms by biological type, such as genus or species. Biological classification is part of scientific taxonomy....
of Celastraceae sensu
Sensu
Sensu is a Latin word meaning "in the sense of".It is used in a number of fields including biology, geology, linguistics, and law. Commonly it refers to how strictly or loosely an expression is used, but it also appears in expressions that indicate the convention or context of the usage.-Sensu and...
APG III has not yet been published.