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Thecolumn, or technically thegynostemium, is a reproductive structure that can be found in several plant families:Aristolochiaceae,Orchidaceae, andStylidiaceae.
It is derived from the fusion of both male and female parts (stamens andpistil) into a single organ.[1] The top part of the column is formed by the anther, which is covered by ananther cap. This means that thestyle andstigma of the pistil, with the filaments and one or more anthers, are all united.
The stigma sits at the apex of the column in the front but is pointing downwards afterresupination (the rotation by 180 degrees before unfolding of the flower).[citation needed]
This stigma has the form of a small bowl, theclinandrium, a viscous surface embedding the (generally) single anther. On top of it all is theanther cap. Sometimes there is a small extension or little beak to the median stigma lobe, calledrostellum.[citation needed]
Column wings may project laterally from the stigma. Thecolumn foot is formed by the attachment of thelip to the basal protruding part of the column. One speaks of amentum (chin) if the lateralsepals are also basally adnate (= attached to the foot of the column).
The column both releasespollen and also receives it (from another individual) for fertilization. In the family Orchidaceae, unlike almost all otherflowering plants, the single male anther at the tip of thecolumn producespollen that is not free and powdery but held in waxy masses of two, four or six pellets calledpollinia. The transfer ofpollinia from one flower to another, though highly efficient, is often reliant upon one particular species ofarthropods and it can be catastrophic for the population if its pollinator disappears from the community.
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