Riella

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Riella
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Kingdom: Plantae
Division: Marchantiophyta
Class: Marchantiopsida
Order: Sphaerocarpales
Family: Riellaceae
Genus: Riella
Mont. 1852 [1]
Species

See classification

Synonyms [2]
  • DuriaeaBory De St. Vincent & Montagne 1843
  • DuriellaBory de St. Vincent ex Billot 1861 non Row 1911 non Dhanam & Jairajpuri 1999
  • MaisonneuveaTrevisan 1877
  • (Trabutiella) Porsild 1902 non Stevens 1920 non Theissen & Sydow 1914

Riella is a genus in the liverwort family Riellaceae, and includes about eighteen species. [3] Plants in the genus are small and grow submerged in shallow temporary pools. Although the genus is widely distributed in the Northern Hemisphere, locating populations is often difficult. Its occurrence is sporadic and local, and the tiny plants are ephemeral. The ornamented spores remain viable for several years, allowing the plants to survive annual drying of their habitat. The plants are easily grown in laboratory cultures. [4]

Contents

Description

Riella plants are small, usually 2 inches (5.1 cm) or less, and thalloid, with an appearance like an immature alga. [3] The plant consists of an erect central axis ("stem") that is commonly forked, [5] but only sparingly, and the plants are bright green. [6]

The stem bears a thin dorsal lamina or "wing", which being on only one side gives the plant an asymmetrical appearance. [7] This lamina is ruffled or undulate. [5] Early descriptions of the species Riella helicophylla overemphasized the spiralled form of the lamina, which does not occur in other species. [8] One species, the Algerian Riella bialata bears two wings along its stems instead of the usual single lamina. [5] The lamina has a thickness of only a single layer of cells, with all the cells thin-walled and chlorophyllose. [9]

In addition to the lamina, the central stem bears delicate, small, leaf-like scales in three series along its lateral and ventral aspects. [4] The leaf scales are dimorphic and contain scattered oil cells, with a single oil body per cell. [6] Riella is thus the only member of its order with oil cells, although other genera in the class Marchantiopsida commonly have them. [10]

Distribution

Although found nearly worldwide, Riella populations are sporadic and limited to only a few known localities. [6] The plants are never common, and are found most often in places where the summer is dry and the winter is wet and mild. [9]

Prior to 1900, Riella was thought to occur only in regions around the Mediterranean. [7] The first collections from outside this region were published in 1902 when Porsild reported collecting R. paulsenii in Kazakhstan in 1898. [11] Three further specimens from the United States were reported in 1903, although one of these had been collected much earlier in 1855. [8] Since that time, additional populations have been reported from South Africa, southern Argentina, and southeastern Australia. [3]

Riella species primarily grow as submerged aquatic plants, rarely floating or emergent. [5] Although it is unique among hepatics as a submerged aquatic, [6] it is not the only aquatic liverwort. [3] The plants grow in fresh or brackish water of temporary bodies of water, and rarely in permanent ones. [6]

Classification

The genus Riella was first published in 1852 by Camille Montagne. [1] The group was given its own family Riellaceae 40 years later by Adolf Engler. [12] Modern bryologists classify the Riellaceae in the order Sphaerocarpales, along with the family Sphaerocarpaceae. [13] Studies comparing genetic sequences of Riella plants support this relationship. [14]

Porsild recognized a subgenus Trabutiella distinguished by the presence of longitudinal wings on the involucre. [11] The only other subgenus (Riella subg. Riella) bears smooth involucres that lack these wings of tissue.

Species of Riella are distinguished using morphology of the spores or archegonial involucres, since the gametophytes of the genus possess few distinguishing non-reproductive characters. [6] There are 19, [9] 18, [3] or 17 species [6] in the genus.

Related Research Articles

Bryophyte Terrestrial plants that lack vascular tissue

Bryophytes are a hypothetical taxonomic division containing three groups of non-vascular land plants (embryophytes): the liverworts, hornworts and mosses. They are characteristically limited in size and prefer moist habitats although they can survive in drier environments. The bryophytes consist of about 20,000 plant species. Bryophytes produce enclosed reproductive structures, but they do not produce flowers or seeds. They reproduce via spores. Though bryophytes were considered a paraphyletic group in recent years, almost all of the most recent phylogenetic evidence supports the monophyly of this group, as originally classified by Wilhelm Schimper in 1879. The term "bryophyte" comes from Greek βρύον, bryon "tree-moss, oyster-green" and φυτόν, phyton "plant".

Marchantiophyta Botanical division of non-vascular land plants that have a gametophyte-dominant life cycle and lack stomata

The Marchantiophyta are a division of non-vascular land plants commonly referred to as hepatics or liverworts. Like mosses and hornworts, they have a gametophyte-dominant life cycle, in which cells of the plant carry only a single set of genetic information.

Marchantiales Order of non-vascular plants known as liverworts

Marchantiales is an order of thallose liverworts that includes species like Marchantia polymorpha, a widespread plant often found beside rivers, and Lunularia cruciata, a common and often troublesome weed in moist, temperate gardens and greenhouses.

Metzgeriales Order of liverwort plants

Metzgeriales is an order of liverworts. The group is sometimes called the simple thalloid liverworts: "thalloid" because the members lack structures resembling stems or leaves, and "simple" because their tissues are thin and relatively undifferentiated. All species in the order have a small gametophyte stage and a smaller, relatively short-lived, spore-bearing stage. Although these plants are almost entirely restricted to regions with high humidity or readily available moisture, the group as a whole is widely distributed, and occurs on every continent except Antarctica.

Lejeuneaceae Family of liverworts

Lejeuneaceae is the largest family of liverworts. Most of its members are epiphytes found in the tropics, while others can be found in temperate regions.

Jungermanniopsida Class of liverworts

Jungermanniopsida is the largest of three classes within the division Marchantiophyta (liverworts).

Monoicous plants are those species that bear both sperm and eggs on the same gametophyte. Dioicous plants are those that have gametophytes that produce only sperm or eggs but never both. The terms are used largely but not exclusively in the context of bryophytes. Both monoicous and dioicous gametophytes produce gametes in gametangia by mitosis rather than meiosis, so that sperm and eggs are genetically identical with their parent gametophyte. The states of being monoicous or dioicous are called monoicy and dioicy respectively.

<i>Cavicularia</i> Genus of liverworts

Cavicularia densa is the only species in the liverwort genus Cavicularia. The species was first described in 1897 by Franz Stephani, and is endemic to Japan, where it grows on fine moist soil.

Treubiaceae Family of liverworts

Treubiaceae is a family of liverworts in the order Treubiales. Species are large and leafy, and were previously classified among the Metzgeriales.

Haplomitriopsida Class of liverworts

Haplomitriopsida is a newly recognized class of liverworts comprising fifteen species in three genera. Recent cladistic analyses of nuclear, mitochondrial, and plastid gene sequences place this monophyletic group as the basal sister group to all other liverworts. The group thus provides a unique insight into the early evolution of liverworts in particular and of land plants in general.

Apotreubia is a genus of liverworts in the family Treubiaceae. There are four species, including: Apotreubia nana, which is found in subalpine New Guinea, and Apotreubia pusilla, which has a disjunct distribution between eastern Asia and British Columbia.

<i>Treubia</i> Genus of liverworts

Treubia is a genus of liverworts in the family Treubiaceae. There are seven species, all of which are restricted to the southern hemisphere. Five of the species occur in Australasia and the other occurs in Chile. All species are dioicous, with separate male and female gametophytes.

Makinoa crispata is the only species of liverwort in the genus Makinoa and family Makinoaceae. The genus Verdoornia was formerly included in this family, but has been transferred to the family Aneuraceae on the basis of recent cladistic analysis of genetic sequences.

<i>Ptilidium</i> Genus of liverworts

Ptilidium is a genus of liverwort, and is the only genus in family Ptilidiaceae. It includes only three species: Ptilidium californicum, Ptilidium ciliare, and Ptilidium pulcherrimum. The genus is distributed throughout the arctic and subarctic, with disjunct populations in New Zealand and Tierra del Fuego. Molecular analysis suggests that the genus has few close relatives and diverged from other leafy liverworts early in their evolution.

Neotrichocoleaceae is a family of liverworts in order Jungermanniales. It is closely related to the genera Ptilidium and Herzogianthus.

Petalophyllaceae is a family of liverworts in the order Fossombroniales. Most species are thallose; that is, the plant is not differentiated into root, stem, and leaf. The thallus is typically small and bears lamellae on its dorsal surface that give it a ruffled, leafy appearance.

Petalophyllum ralfsii, the petalwort, is a liverwort of the order Fossombroniales. It is a small green bryophyte that occurs in the Mediterranean region as far east as Turkey, and along the Atlantic coast of Europe as far as northwest Scotland. It grows primarily on moist sand dunes.

Petalophyllum, or petalwort, is a genus of liverworts in the order Fossombroniales.

Petalophyllum americanum, common name petalwort, is a species of liverwort in the order Fossombroniales. It is endemic to the Gulf Coast of the United States in Arkansas, Louisiana, Mississippi, and Texas. It was first described as the European species Petalophyllum ralfsii in 1919, but a detailed study later showed that the North American form is a distinct species.

<i>Ricciocarpos</i> Genus of liverworts

Ricciocarpos natans is the only species in the genus Ricciocarpos, a genus of liverworts in the family Ricciaceae. It was formerly listed in 1759 as a species of Riccia by Linnaeus, but then assigned to a new genus of its own in 1829 by August Carl Joseph Corda.

References

  1. 1 2 Montagne, C. (1852). "Note sur le genre Riella, et description d'une espèce nouvelle, R. Reuteri". Annales des Sciences Naturelles. Sér. 3 (Botanique). 18: 11–13.
  2. ↑ "Part 2- Plantae (starting with Chlorophycota)". Collection of genus-group names in a systematic arrangement. Archived from the original on 16 August 2018. Retrieved 30 June 2016.
  3. 1 2 3 4 5 Schuster, Rudolf M. (1992). The Hepaticae and Anthocerotae of North America. V. Chicago: Field Museum of Natural History. pp. 827–844. ISBN   0-914868-20-9.
  4. 1 2 Bold, Harold C.; Alexopoulos, C. J.; Delevoryas, T. (1987). Morphology of Plants and Fungi (5th ed.). New York: Harper-Collins. pp. 216–218. ISBN   0-06-040839-1.
  5. 1 2 3 4 Haynes, Caroline Coventry; Howe, Marshall Avery (1923). "Riellaceae". North American Flora. 14 (1): 7–8.
  6. 1 2 3 4 5 6 7 Bartholomew-Began, S. E. "Riella". Bryophyte Flora of North America. Retrieved 26 June 2011.
  7. 1 2 Campbell, Douglas H. (1918). The Structure and Development of Mosses and Ferns (revised ed.). London: The Macmillan Co. pp.  73-75, 83–74.
  8. 1 2 Howe, M. A.; Underwood, L. M. (1903). "The Genus Riella with Descriptions of new Species from North America and the Canary Islands". Bulletin of the Torrey Botanical Club. 30 (4): 214–224. doi:10.2307/2478779.
  9. 1 2 3 Schofield, W. B. (1985). Introduction to Bryology. New York: Macmillan. pp. 197–206. ISBN   0-02-949660-8.
  10. ↑ Crandall-Stotler, Barbara; Stotler, Raymond E. (2000). "Morphology and classification of the Marchantiophyta". In A. Jonathan Shaw; Bernard Goffinet (eds.). Bryophyte Biology. Cambridge: Cambridge University Press. pp. 21–70. ISBN   0-521-66097-1.
  11. 1 2 Porsild, M. P. (1902). "Sur une nouvelle espèce de Riella (subgen. nov.: Trabutiella) de l'Asie centrale". Bot. Tidsskr. 24: 323–327.
  12. ↑ Engler, A. (1892). Syllabus der Pflanzenfamilien. 1 (Grosse Ausgabe, 1st ed.). p. 45.
  13. ↑ Grolle, Riclef (1983). "Nomina generica Hepaticarum; references, types and synonymies". Acta Botanica Fennica. 121: 1–62.
  14. ↑ Forrest, Laura L.; Christine E. Davis; David G. Long; Barbara J. Crandall-Stotler; Alexandra Clark; Michelle L. Hollingsworth (2006). "Unraveling the evolutionary history of the liverworts (Marchantiophyta): multiple taxa, genomes and analyses". The Bryologist. 109 (3): 303–334. doi:10.1639/0007-2745(2006)109[303:UTEHOT]2.0.CO;2.
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