Tribe Neottieae - The Pollination Biology of North American Orchids: North of Florida and Mexico - page 63

flowers of Cephalanthera are sessile and the ovary is spirally twisted, whereas those
of Epipactis are stalked and the pedicels are long enough to include most of the
twist of resupination (Luer 1975 ). The common name “Helleborine” is still often
applied to both, and natural intergeneric hybrids occur (Dressler 1993 ).
Cephalanthera Richard
Cephalanthera is a genus of about 15 species found in North Africa, temperate
%URASIAANDWESTERN.ORTH!MERICA0RIDGEONETAL 2005 ). A single species is rep-
resented in our flora.
Cephalanthera austinae (A. Gray) A. Heller
(Phantom Orchid, Snow Orchid)
Habitat and Distribution
C. austinae is a perennial, achlorophyllous plant totally dependent on mycorrhizal
fungi for survival. It is found in coniferous forests on dry to moist mineral soils from
southern British Columbia and northern Idaho to California (Sheviak and Catling
2002 ).
Floral Morphology
Variable numbers of resupinate flowers are borne in a loose, terminal raceme
(Table 3.2 ). Like the rest of the plant, they are essentially pure white, except for a
yellow mark on the lip (Kipping 1971 ; Luer 1975 ). The lateral sepals are spreading
while the petals are partially connivent with the hood-like dorsal sepal (Fig. 3.3a ).
The lip is constricted in the center, giving rise to distal and basal sections (Fig. 3.3b ).
The basal section (hypochile) is concave with triangular lateral lobes that curve
upward to flank the column. The distal section (epichile) is deflexed and cordate
with a rounded apex and a yellow center. Its dorsal surface bears three to five, fine
longitudinal ridges (Fig. 3.3b ); these are ciliated, yellow or orange in color, and
thought by some to represent pseudopollen (Kipping 1971 ; Luer 1975 ; van der
Cingle 2001 ; Sheviak and Catling 2002 ). The flowers produce neither scent
nor nectar. The column is slender, upright, and nearly round in cross section. The
anther is dorsal, and two pairs of soft, elongate pollinia are present under a hinged
anther cap at the end of the column (Fig. 3.3c, d ). Each pollinium comprises two
granular strands of white, mealy pollen. The stigma, made up of three functional,
confluent lobes, is positioned immediately below the anther (Fig. 3.3c, d ) (Kipping
1971 ; Luer 1975 ; Sheviak and Catling 2002 0RIDGEONETAL 2005 ). The pollinia
have no caudicle and are commonly said to also lack a viscidium and rostellum