A cyathium (: cyathia) is one of the specialised pseudanthia ("false flowers") forming the

inflorescence In botany, an inflorescence is a group or cluster of flowers arranged on a plant's Plant stem, stem that is composed of a main branch or a system of branches. An inflorescence is categorized on the basis of the arrangement of flowers on a mai ...

of plants in the genus ''

Euphorbia ''Euphorbia'' is a large and diverse genus of flowering plants, commonly called spurge, in the family (biology), family Euphorbiaceae. Euphorbias range from tiny annual plants to large and long-lived trees, with perhaps the tallest being ''Eu ...

'' (

Euphorbiaceae Euphorbiaceae (), the spurge family, is a large family of flowering plants. In English, they are also commonly called euphorbias, which is also the name of Euphorbia, the type genus of the family. Most spurges, such as ''Euphorbia paralias'', ar ...

). A cyathium consists of: * Five (rarely four) bracteoles. These are small, united

bract In botany, a bract is a modified or specialized leaf, associated with a reproductive structure such as a flower, inflorescence axis or cone scale. Bracts are usually different from foliage leaves in size, color, shape or texture. They also lo ...

s, which form a cup-like involucre. Their upper tips are free and cover the opening of the involucre (like the shutter of a camera). These alternate with: * Five (1 to 10) nectar glands, which are sometimes fused. * One extremely reduced female flower standing in the centre on a stalk at the base of the involucre surrounded by: * Four or five groups (one group at the base of each bracteole) of extremely reduced male flowers, which each consist of a single

anther The stamen (: stamina or stamens) is a part consisting of the male reproductive organs of a flower. Collectively, the stamens form the androecium., p. 10 Morphology and terminology A stamen typically consists of a stalk called the filament ...

on a stem. The flower-like characteristics of the cyathia are underlined by brightly coloured nectar glands and often by

petal Petals are modified leaves that form an inner whorl surrounding the reproductive parts of flowers. They are often brightly coloured or unusually shaped to attract pollinators. All of the petals of a flower are collectively known as the ''corol ...

-like appendages to the nectar glands, or brightly coloured, petal-like bracts positioned under the cyathia. The paired petal-like bracts of ''Euphorbia'' section ''Goniostema'' are called ''cyathophylls''. here female to male flower ratio is 1:α The cyathia are sometimes solitary, but are usually in

cymes In botany, an inflorescence is a group or cluster of flowers arranged on a plant's stem that is composed of a main branch or a system of branches. An inflorescence is categorized on the basis of the arrangement of flowers on a main axis ( ped ...

inflorescences In botany, an inflorescence is a group or cluster of flowers arranged on a plant's stem that is composed of a main branch or a system of branches. An inflorescence is categorized on the basis of the arrangement of flowers on a main axis ( pe ...

of the second order, in pseudumbels, on dichotomously branched stalks or in so-called simple cymes which consist of one central and two lateral cyathia. In one group of Madagascan species in the subfamily Euphorbia section Goniostema (''E. aueoviridiflora'', ''E. capmanambatoensis'', ''E. iharanae'', ''E. leuconeura'', ''E. neohumbertii'', ''E. viguieri'') there is a tendency for a further pseudanthium to grow from the cyme. Probably as an adaptation to pollination by

bird Birds are a group of warm-blooded vertebrates constituting the class (biology), class Aves (), characterised by feathers, toothless beaked jaws, the Oviparity, laying of Eggshell, hard-shelled eggs, a high Metabolism, metabolic rate, a fou ...

s, the cyathia have become specialised: Most cyathia have upright cyathophylls which surround them protectively, but render the nectar glands inaccessible. To compensate, between them are naked sterile cyathia whose only job is to produce nectar.

References

* Sandro Pignatti, Flora d'Italia, Edagricole, Bologna 1982. {{ISBN, 88-506-2449-2 Plant morphology Euphorbia