Tribe Neottieae - The Pollination Biology of North American Orchids: North of Florida and Mexico - page 66

Fruiting Success and Limiting Factors
Kipping ( 1971 ) found that 15-27% of open-pollinated flowers produced fruit over
the course of his 2-year study in northern California. Data on specific factors that
may affect fruit set in this orchid are not yet available, but the percentages observed
in unmanipulated caged (14-30%) versus open-pollinated flowers imply that autog-
amy is frequent in this population.
Epipactis Zinn
The genus Epipactis INCLUDES0RIDGEONETAL 2005 ) to 30 (Thornhill 1996 ) tem-
perate Eurasian and African species. One is native to North America and Asia. Two
others are introduced to our flora.
Epipactis gigantea Douglas ex Hooker
(Giant Helleborine, Stream Orchid)
Habitat and Distribution
This native, North American orchid requires a continuous water supply for its roots
and is often found along shores on wet gravely substrates and sand bars or seepage
banks (Coleman 1995 ). It also occurs around springs and in riparian woodlands or
chaparral. It is distributed from British Columbia to southern California west to
Montana and Texas with isolated populations in Oklahoma and southwestern South
Dakota (Coleman 1995 ; Brown and Argus 2002 ).
Floral Morphology
Two to thirty-two rather showy, resupinate flowers are borne in an often one-sided,
lax raceme (Table 3.3 ) (Coleman 1995 ; Brown and Argus 2002 ). The sepals are
often greenish-yellow with purple veins. The laterals are widely spreading
(Fig. 3.4a ). The petals extend forward over the column and are usually pale pink to
reddish or orange with darker red or purple veins. As in Cephalanthera, a central
constriction divides the lip transversely into two parts (Fig. 3.4a ). The basal part
(hypochile) is concave with centrally located, small, warty calli and subtriangular
lateral lobes. The calli are red to yellow, and the lobes are yellowish with purple to
brown veins. The distal part (epichile), hinged and mobile, is oblanceolate and
grooved to a pink apex. Two erect, wing-like, yellow-orange calli are again present
near the base. The column is erect. The stigma and rostellum are positioned between
a pair of lateral processes below the anther cap (Fig. 3.4b, c ) (Luer 1975 ). The anther