Tribe Malaxideae - The Pollination Biology of North American Orchids: North of Florida and Mexico - page 100

and North Carolina. A number of more westerly and southerly disjunct populations
are spread from Alabama to Washington and the Northwest Territories (Scoggan
1978 ; McMaster 2001 ; Magrath 2002 ). It is most commonly found in alkaline or
circumneutral substrates in a wide range of habitats (Luer 1975 ; Catling 1980 ).
These can include moist ravines, bogs, fens, wet meadows, forested wetlands, seeps,
and dune slacks as well as dryer upland sites. Like the preceding species, it often
shows a preference for early successional stages and disturbed areas (McLain 1968 ;
Catling 1980 ; Thompson and MacGregor 1986 ).
Floral Morphology
Up to 19 very small, white to greenish, resupinate flowers are borne in a single loose
raceme (Table 5.2 ) (McMaster 2001 and references therein). The sepals are spread-
ing or directed forward, and the petals are pendant to spreading; both have revolute
margins (Fig. 5.4a ) (Luer 1975 ; Magrath 2002 ). The lip is obovate or suborbiculate
to oblong and arcuate recurved with an obtuse to apiculate apex and crenulate-wavy
margins. It is translucent to opaque, green to yellowish, and thickened down the
center (Luer 1975 ; Magrath 2002 ). An incurved column bears wing-like projections
on its upper part (Fig. 5.4e, f ). Two pairs of waxy, yellow pollinia are contained
within a two-celled terminal anther (Fig. 5.4f ) (von Kirchner 1922 ; Luer 1975 ).
A well-developed caudicle and viscidium are absent. The flowers produce no nectar
and lack a perceptible odor (von Kirchner 1922 ).
Compatibility and Breeding System
L. loeselii is self-compatible and autogamous (von Kirchner 1922 ; Hagerup 1941 ;
Catling 1980 ). In a study of plants from York County, Ontario, Catling ( 1980 ) estab-
lished seven treatment groups. All were held in a large insect-proof enclosure in the
greenhouse while in flower. Flowers in the first group were maintained as a control.
In the second, they were emasculated, in the third they were vigorously agitated by
“wind” from a strong fan, and in the fourth they were sprayed for 5 min with water
from a watering can (fine spray) and hose (heavy spray) once every 2 days over the
course of the 3-week flowering period. In the fifth, sixth, and seventh groups, the
flowers were artificially fertilized by self-pollination, geitonogamous pollination,
and cross-pollination, respectively.
No seed developed in emasculated flowers suggesting the absence of aga-
mospermy. Artificial self-, geitonogamous-, and cross-pollinations produced seed in
94-100% of the ovaries tested compared to 17% in undisturbed (control) plants.
Flowers agitated by “wind” did not differ from undisturbed plants in their levels of
autogamous pollination. However, flowers receiving the simulated rain treatment
(group 4) had quadruple the level of autogamy (viz. 70%) found in undisturbed
plants watered from below (Catling 1980 ).