''Cartonema'' is a genus of perennial or annual

monocotyledon Monocotyledons (), commonly referred to as monocots, (Lilianae ''sensu'' Chase & Reveal) are grass and grass-like flowering plants (angiosperms), the seeds of which typically contain only one embryonic leaf, or cotyledon. They constitute one of ...

ous

flowering plant Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek words ('container, vessel') and ('seed'), and refers to those plants th ...

s in the dayflower family. It is restricted to Australia and nearby Trangan Island, which is part of

Indonesia Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania between the Indian and Pacific oceans. It consists of over 17,000 islands, including Sumatra, Java, Sulawesi, and parts of Borneo and New Guine ...

. It is the earliest diverging member of its family and has a number of traits that are unique within it, such as non- succulent leaves and a lack of

raphide Raphides (pronounced /ˈræfɪˌdiz/, singular raphide /ˈreɪfʌɪd/ or raphis) are needle-shaped crystals of calcium oxalate monohydrate (prismatic monoclinic crystals) or calcium carbonate as aragonite ( dipyramidal orthorhombic crystals), fo ...

s (a particular form of calcium oxalate). Its distinctive features led to the genus to once be considered part of its own separate family, Cartonemataceae. However, analysis of

DNA sequences A nucleic acid sequence is a succession of bases signified by a series of a set of five different letters that indicate the order of nucleotides forming alleles within a DNA (using GACT) or RNA (GACU) molecule. By convention, sequences are us ...

, as well as many common anatomical characters, has supported its relationship with the

Commelinaceae Commelinaceae is a family of flowering plants. In less formal contexts, the group is referred to as the dayflower family or spiderwort family. It is one of five families in the order Commelinales and by far the largest of these with about 731 kno ...

. It contains about 11 species.

Description

Plants in the genus may be either annuals or perennials, and in the latter case they sometimes have

tuber Tubers are a type of enlarged structure used as storage organs for nutrients in some plants. They are used for the plant's perennation (survival of the winter or dry months), to provide energy and nutrients for regrowth during the next growin ...

s. The leaves are spirally arranged, lack a leaf stalk, and are covered in glandular hairs; the leaf blade is linear. Flowers are borne on an

inflorescence An inflorescence is a group or cluster of flowers arranged on a Plant stem, stem that is composed of a main branch or a complicated arrangement of branches. Morphology (biology), Morphologically, it is the modified part of the shoot of sperma ...

that either occurs along the main shoot or at its terminus, in the form of either a

spike Spike, spikes, or spiking may refer to: Arts, entertainment, and media Books * ''The Spike'' (novel), a novel by Arnaud de Borchgrave * ''The Spike'' (book), a nonfiction book by Damien Broderick * ''The Spike'', a starship in Peter F. Hamilto ...

or a raceme. As with all members of the family

, the ultimate inflorescence unit is a cincinnus, also called scorpioid cymes, which are monochasiums (i.e. cymes with a single branched main false axis) in which the lateral branches arise alternately on opposite sides of the false axis. However, in ''Cartonema'' the cincinnus is highly reduced such that each only bears one flower. The flowers are bisexual,

radially symmetrical Symmetry in biology refers to the symmetry observed in organisms, including plants, animals, fungi, and bacteria. External symmetry can be easily seen by just looking at an organism. For example, take the face of a human being which has a pla ...

, and lack a stalk. The

sepal A sepal () is a part of the flower of angiosperms (flowering plants). Usually green, sepals typically function as protection for the flower in bud, and often as support for the petals when in bloom., p. 106 The term ''sepalum'' was coine ...

s are not fused and bear glandular hairs, while the petals are yellow to pink (in rare cases) and are also unfused. They bear six fertile stamens which have no hairs on their filaments and release pollen from a slit that develops from top to bottom, known as longitudinal dehiscence. The ovary is composed of three

carpel Gynoecium (; ) is most commonly used as a collective term for the parts of a flower that produce ovules and ultimately develop into the fruit and seeds. The gynoecium is the innermost whorl of a flower; it consists of (one or more) '' pistils' ...

s with two or more

ovule 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'' (or remnant of the megasporangium), and the ...

s in each. The

fruit In botany, a fruit is the seed-bearing structure in flowering plants that is formed from the ovary after flowering. Fruits are the means by which flowering plants (also known as angiosperms) disseminate their seeds. Edible fruits in particu ...

is a capsule opening with three valves. The seeds are arranged in a single row within the capsule and show a small point-like scar where previously attached to the carpel (i.e. the hilum is punctiform). The diploid

chromosome A chromosome is a long DNA molecule with part or all of the genetic material of an organism. In most chromosomes the very long thin DNA fibers are coated with packaging proteins; in eukaryotic cells the most important of these proteins are ...

number is 24. ''Cartonema'' is distinct from the rest of the dayflower family in a number of important features. They lack internal

raphides Raphides (pronounced /ˈræfɪˌdiz/, singular raphide /ˈreɪfʌɪd/ or raphis) are needle-shaped crystals of calcium oxalate monohydrate ( prismatic monoclinic crystals) or calcium carbonate as aragonite ( dipyramidal orthorhombic crystals), ...

, calcium oxalate crystals in a needle-like shape, which all other members of the family have. They lack glandular microhairs, which are small

trichome Trichomes (); ) are fine outgrowths or appendages on plants, algae, lichens, and certain protists. They are of diverse structure and function. Examples are hairs, glandular hairs, scales, and papillae. A covering of any kind of hair on a p ...

s thought to be involved in the lubrication of freshly expanding leaves, which again all of the plants' siblings have. Finally, they have yellow flowers and glandular hairs on the leaves and stems; these characters are not unheard of in the rest of the family, but both are very rare.

References

External links

* *
Profile of ''Cartonema'' at the Flora of Western Australia's FloraBase
{{Taxonbar, from=Q5047396 Commelinales genera Taxa named by Robert Brown (botanist, born 1773)