Tribe Pogonieae - The Pollination Biology of North American Orchids: North of Florida and Mexico - page 177

Fig. 9.4 Cleistesiopsis . ( a ) C. bifaria , flower, side view (sepal orientation variable); ( b ) Generalized
column for C. divaricata and C. bifaria , side view with small protrusion on underside of anther
cap; scale bars = 5 mm. an anther, ro rostellum, sg stigmatic area
selfing and geitonogamy reduced the percentage of healthy embryos. Vegetative
propagation by root shoots is common (Gregg 1991c ).
The two species of Cleistesiopsis are interfertile and artificial crosses between
them did not result in lower seed production than crosses within the parental species
(Catling and Gregg 1992 ). However, naturally occurring hybrids were not
observed.
Pollinators and Pollination Mechanisms
Although insect visits were rare, bumblebees ( Bombus spp.) in North Carolina and
both bumblebees and leaf-cutter bees ( Megachile spp.) in West Virginia are the
primary pollinators of Cleistesiopsis (Gregg 1989, 1991b ). The bee, usually a
worker, first lands on the labellum and crawls toward its base. As it passes beneath
the column, its head and dorsal thorax touch the stigma and are smeared with sticky,
stigmatic fluid. On backing out of the flower its back contacts a small protrusion on
the underside of the anther (Fig. 9.4b ). The hinged anther cap is pulled open and
clumps of loosely coherent tetrads are dumped onto the stigmatic fluid covering the
bee's dorsal thorax and head. The anther cap then snaps back to its original position.
On later floral visits, the dorsal thorax and head contact the stigma and pollen is