Rostellum
Encyclopedia
The rostellum is a projecting part of the column
in Orchidaceae
flowers, and separates the male stamen
from the female gynoecium
, commonly preventing self-fertilisation. In many orchids, such as Orchis mascula, the pollinia
or pollen masses, are connected by stipes
down to adhesive discs attached to the rostellum which forms cups keeping the discs or balls sticky.
In Catasetum
flowers the rostellum projects forward at each side as an "antenna", and the pollen masses are connected by a bent stalk or pedicel
to a sticky disc kept moist at the back of the flower. When an insect touches an "antenna", this releases the bent pedicel which springs straight and fires the pollinium, sticky disc first, at the insect. Charles Darwin
described in Fertilisation of Orchids
how he "touched the antennæ of C. callosum whilst holding the flower at about a yard's distance from the window, and the pollinium hit the pane of glass, and adhered to the smooth vertical surface by its adhesive disc."
Column (botany)
The column, or technically the gynostemium, is a reproductive structure that can be found in several plant families: Aristolochiaceae, Orchidaceae, and Stylidiaceae....
in Orchidaceae
Orchidaceae
The Orchidaceae, commonly referred to as the orchid family, is a morphologically diverse and widespread family of monocots in the order Asparagales. Along with the Asteraceae, it is one of the two largest families of flowering plants, with between 21,950 and 26,049 currently accepted species,...
flowers, and separates the male stamen
Stamen
The stamen is the pollen producing reproductive organ of a flower...
from the female gynoecium
Gynoecium
Gynoecium is most commonly used as a collective term for all carpels in a flower. A carpel is the ovule and seed producing reproductive organ in flowering plants. Carpels are derived from ovule-bearing leaves which evolved to form a closed structure containing the ovules...
, commonly preventing self-fertilisation. In many orchids, such as Orchis mascula, the pollinia
Pollinium
Pollinium, or plural pollinia, is a coherent mass of pollen grains in a plant.They are the product of only one anther, but are transferred, during pollination, as a single unit. This is regularly seen in plants such as orchids and many species of milkweeds .Most orchids have waxy pollinia...
or pollen masses, are connected by stipes
Stipe (botany)
In botany, a stipe is a stalk that supports some other structure. The precise meaning is different depending on which taxonomic group is being described....
down to adhesive discs attached to the rostellum which forms cups keeping the discs or balls sticky.
In Catasetum
Catasetum
Catasetum, abbreviated as Ctsm in horticultural trade, is a genus of the Orchid family , subfamily Epidendroideae, tribe Cymbidieae, subtribe Catasetinae, with 166 species....
flowers the rostellum projects forward at each side as an "antenna", and the pollen masses are connected by a bent stalk or pedicel
Pedicel (botany)
A pedicel is a stem that attaches single flowers to the main stem of the inflorescence. It is the branches or stalks that hold each flower in an inflorescence that contains more than one flower....
to a sticky disc kept moist at the back of the flower. When an insect touches an "antenna", this releases the bent pedicel which springs straight and fires the pollinium, sticky disc first, at the insect. Charles Darwin
Charles Darwin
Charles Robert Darwin FRS was an English naturalist. He established that all species of life have descended over time from common ancestry, and proposed the scientific theory that this branching pattern of evolution resulted from a process that he called natural selection.He published his theory...
described in Fertilisation of Orchids
Fertilisation of Orchids
Fertilisation of Orchids is a book by Charles Darwin published on 15 May 1862 under the full explanatory title On the various contrivances by which British and foreign orchids are fertilised by insects, and on the good effects of intercrossing...
how he "touched the antennæ of C. callosum whilst holding the flower at about a yard's distance from the window, and the pollinium hit the pane of glass, and adhered to the smooth vertical surface by its adhesive disc."