The column, or technically the gynostemium, is a reproductive structure that can be found in several plant families:

Aristolochiaceae The Aristolochiaceae () are a family, the birthwort family, of flowering plants with seven genera and about 400 known species belonging to the order Piperales. The type genus is ''Aristolochia'' L. Description They are mostly perennial, he ...

Orchidaceae Orchids are plants that belong to the family Orchidaceae (), a diverse and widespread group of flowering plants with blooms that are often colourful and fragrant. Along with the Asteraceae, they are one of the two largest families of flowerin ...

, and Stylidiaceae. It is derived from the fusion of both male and female parts (

stamen The stamen (plural ''stamina'' or ''stamens'') is the pollen-producing reproductive organ of a flower. Collectively the stamens form the androecium., p. 10 Morphology and terminology A stamen typically consists of a stalk called the fila ...

s and pistil) into a single organ. The top part of the column is formed by the anther, which is covered by an anther cap. This means that the ''style'' and ''stigma'' of the pistil, with the filaments and one or more anthers, are all united.

Orchidaceae

The stigma sits at the apex of the column in the front but is pointing downwards after resupination (the rotation by 180 degrees before unfolding of the flower). This stigma has the form of a small bowl, the clinandrium, a viscous surface embedding the (generally) single anther. On top of it all is the anther cap. Sometimes there is a small extension or little beak to the median stigma lobe, called

rostellum The rostellum is a projecting part of the column in Orchidaceae flowers, and separates the male androecium from the female gynoecium, commonly preventing self-fertilisation. In many orchids, such as '' Orchis mascula'', the pollinia or pollen ma ...

. Column wings may project laterally from the stigma. The column foot is formed by the attachment of the lip to the basal protruding part of the column. One speaks of a mentum (chin) if the lateral

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 also basally adnate (= attached to the foot of the column). The column both releases pollen and also receives it (from another individual) for fertilization. In the family Orchidaceae, unlike almost all other

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 t ...

s, the single male anther at the tip of the ''column'' produces pollen that is not free and powdery but held in waxy masses of two, four or six pellets called '' pollinia''. The transfer of ''pollinia'' from one flower to another, though highly efficient, is often reliant upon one particular species of

arthropod Arthropods (, (gen. ποδός)) are invertebrate animals with an exoskeleton, a segmented body, and paired jointed appendages. Arthropods form the phylum Arthropoda. They are distinguished by their jointed limbs and cuticle made of chiti ...

s and it can be catastrophic for the population if its pollinator disappears from the community.

References

{{botany Plant morphology Pollination Orchid morphology