Christensenia
Encyclopedia
Christensenia is a genus
of fern
s in the botanical
family
Marattiaceae. The genus is confined to the Indo-Malayan region. The basal chromosome number
for this genus is 2n=80.
Christensenia is unique in the Marattiaceae, because of its reticulate venation, palmately arranged leaves and radial synangia. Christensenia produces enormous amounts of spore
s, up to 7,000 spores per sporangium
.
The presence of a radial synangium is an archaic character, very similar to some of the fossil
Asterothecaceae/Psaroniaceae, such as Scolecopteris. Christensenia itself has no fossil record.
and one variety are recognized:
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...
of fern
Fern
A fern is any one of a group of about 12,000 species of plants belonging to the botanical group known as Pteridophyta. Unlike mosses, they have xylem and phloem . They have stems, leaves, and roots like other vascular plants...
s in the botanical
Botany
Botany, plant science, or plant biology is a branch of biology that involves the scientific study of plant life. Traditionally, botany also included the study of fungi, algae and viruses...
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...
Marattiaceae. The genus is confined to the Indo-Malayan region. The basal chromosome number
Karyotype
A karyotype is the number and appearance of chromosomes in the nucleus of an eukaryotic cell. The term is also used for the complete set of chromosomes in a species, or an individual organism.p28...
for this genus is 2n=80.
Christensenia is unique in the Marattiaceae, because of its reticulate venation, palmately arranged leaves and radial synangia. Christensenia produces enormous amounts of spore
Spore
In biology, a spore is a reproductive structure that is adapted for dispersal and surviving for extended periods of time in unfavorable conditions. Spores form part of the life cycles of many bacteria, plants, algae, fungi and some protozoa. According to scientist Dr...
s, up to 7,000 spores per sporangium
Sporangium
A sporangium is an enclosure in which spores are formed. It can be composed of a single cell or can be multicellular. All plants, fungi, and many other lineages form sporangia at some point in their life cycle...
.
The presence of a radial synangium is an archaic character, very similar to some of the fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
Asterothecaceae/Psaroniaceae, such as Scolecopteris. Christensenia itself has no fossil record.
Species
After the 1993 revision by Rolleri, only two speciesSpecies
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...
and one variety are recognized:
- Christensenia aesculifolia (BlumeCarl Ludwig BlumeCharles Ludwig de Blume or Karl Ludwig von Blume was a German-Dutch botanist.He was born at Braunschweig in Germany, but studied at Leiden University and spent his professional life working in the Dutch East Indies and in the Netherlands, where he was Director of the Rijksherbarium at Leiden...
) MaxonWilliam Ralph MaxonWilliam Ralph Maxon, was an American botanist and pteridologist. He graduated from Syracuse University with a Ph.B. in 1898, and spent about one year at Columbia University doing post-graduate work on ferns with Lucien Marcus Underwood...
(type speciesType speciesIn biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...
)- Christensenia aesculifolia var. korthalsii
- Christensenia lobbiana (de VrieseWillem Hendrik de VrieseWillem Hendrik de Vriese was a Dutch botanist and physician born in Oosterhout, North Brabant.He studied medicine at the University of Leiden, earning his doctorate in 1831. Afterwards he practiced medicine in Rotterdam, where he also gave classes in botany at the medical school...
) Rolleri