Oncocalamus
Encyclopedia
Oncocalamus is a monoecious genus
of flowering plant
in the palm
family found in western Africa
. The genus is the lone member of the Oncocalaminae; once placed with the vegetatively similar Eremospatha
and Laccosperma
in the Ancistrophyllinae, it is now isolated based on their unusual flowers and arrangement. Such a placement argues for a long and complex evolutionary process in the Calamoideae with heavy extinction rates. The Greek
genus name combines "horn" and "capsule".
which become pinnate
in maturity, with leaf sheath spines, leaflet cirri, and spiny petioles, all adapted for climbing. The leaflets are few to many, with one, two, or more folds, entire, acute, linear or sigmoid, and regularly arranged along the rachis.
As hapaxanth
s, the inflorescence
emerges at the top of the stem, amongst reduced leaves, with male and female flower
s, on a once-branched spike. The flowers are arranged in clusters of up to 11, with one or three pistillate and two to four staminate flowers at the center of the cluster. The fruit
is spherical and covered in vertical rows of yellow to brown scales with one seed
.
ial west Africa
.
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 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...
in the palm
Arecaceae
Arecaceae or Palmae , are a family of flowering plants, the only family in the monocot order Arecales. There are roughly 202 currently known genera with around 2600 species, most of which are restricted to tropical, subtropical, and warm temperate climates...
family found in western Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
. The genus is the lone member of the Oncocalaminae; once placed with the vegetatively similar Eremospatha
Eremospatha
Eremospatha is a climbing genus of flowering plant in the palm family found in tropical Africa. These rattans are uncommon in cultivation and poorly understood by taxonomists; some 12 species have been described, of which three are commonly recognized. Closely related to Laccosperma, they are...
and Laccosperma
Laccosperma
Laccosperma is a clustering genus of flowering plant in the palm family found in tropical Africa. Poorly studied and rarely cultivated, they are closely related to the Eremospatha genus and with it form a tribe in the Calameae characterized by dyads of hermaphrodite flowers...
in the Ancistrophyllinae, it is now isolated based on their unusual flowers and arrangement. Such a placement argues for a long and complex evolutionary process in the Calamoideae with heavy extinction rates. The 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;...
genus name combines "horn" and "capsule".
Description
The trunks are small, very spiny, and high climbing, becoming bare with age. All species form dense clusters with undivided or bifid juvenile leavesLeaf
A leaf is an organ of a vascular plant, as defined in botanical terms, and in particular in plant morphology. Foliage is a mass noun that refers to leaves as a feature of plants....
which become pinnate
Pinnate
Pinnate is a term used to describe feather-like or multi-divided features arising from both sides of a common axis in plant or animal structures, and comes from the Latin word pinna meaning "feather", "wing", or "fin". A similar term is pectinate, which refers to a comb-like arrangement of parts...
in maturity, with leaf sheath spines, leaflet cirri, and spiny petioles, all adapted for climbing. The leaflets are few to many, with one, two, or more folds, entire, acute, linear or sigmoid, and regularly arranged along the rachis.
As hapaxanth
Hapaxanth
A hapaxanth is a term used for a plant species whose individuals flowers only once in their lifetime and die subsequently. Other terms with the same meaning are semelparous and monocarpic....
s, 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...
emerges at the top of the stem, amongst reduced leaves, with male and female 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, on a once-branched spike. The flowers are arranged in clusters of up to 11, with one or three pistillate and two to four staminate flowers at the center of the cluster. 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 spherical and covered in vertical rows of yellow to brown scales with one 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...
.
Distribution and habitat
Strictly low land rain forest inhabitants, they are found in equatorEquator
An equator is the intersection of a sphere's surface with the plane perpendicular to the sphere's axis of rotation and containing the sphere's center of mass....
ial west Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
.