Tribe Malaxideae - The Pollination Biology of North American Orchids: North of Florida and Mexico - page 101

Fig. 5.4 Liparis loeselii. ( a ) Flower, slightly oblique view, scale bar = 2 mm; ( b )-( d ) movements
leading to autogamy; ( b ) elevation of the anther cap (cf. “ e ”); ( c ) pollen masses (represented dia-
grammatically as a single unit) rotate out of the anther to lower margin of the rostellum; ( d ) quick
downward movement of the anther cap pushes pollinia onto the stigmatic surface, scale bar =
0.5 mm; ( e ) column, side view; ( f ) column, front view, scale bar = 0.5 mm. an anther, po pollinium,
ro rostellum, sg stigma, wi wing
Pollination Mechanism and Pollinators
Catling ( 1980 ) saw no insects visiting the flowers in York County despite 30 h of
observation during the period of peak flowering. One to four days after anthesis the
anther cap began to disintegrate and turn brown. Browning was accompanied by an
elevation of the cap at its point of attachment on the top of the column probably due
to a contraction of dead tissue (Fig. 5.4b ). Its elevation released the pollen masses,
permitting them to rotate or slide out of the anther compartments to the lower mar-
gin of the rostellum, where a small ridge separated the upper surface of the column
from the stigma (Fig. 5.4c ). A small deposit of adhesive material usually held the
pollinia in this position, but in 17% of the flowers rotation onto the stigmatic surface
occurred directly. If water droplets from an eyedropper were made to fall on the
anther cap, the cap was forced quickly downward, pushing the pollinia around
the edge of the margin onto the stigmatic surface (Fig. 5.4d ). The pollen masses
were also pulled onto the stigma by cohesive forces as the water droplets were
slowly reduced in size by evaporation or as they ran rapidly over the flower surface.