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(Ackerman 1975 ; Kallunki 1981 ). They are able to access the recessed nectar source,
likely to be beyond the reach of smaller, short-tongued bees, and are strong enough
to inadvertently rupture the rostellum (Kipping 1971 ).
Kipping ( 1971 ) recorded pollen-bearing workers of Bombus vosnesenskii
Radoszkowski visiting flowers of G . oblongifolia in Nevada County, California.
Another visitor, B. mixtus Cresson, carried no pollinaria (Kipping 1971 ). Ackerman
( 1975 OBSERVEDANDCAPTUREDPOLLENBEARINGQUEENSOF B . occidentalis Greene on
this orchid in Humboldt County. The bumblebees here were few in number, were
SEENMOSTLYONSUNNYDAYSANDQUICKLYEXAMINEDSEVERALmOWERSONEACHINmORES-
cence before departing.
Kallunki ( 1976, 1981 ) also described bumblebees systematically visiting and
removing pollinaria from the flowers of Goodyera in Michigan. She observed
Bombus perplexus on G. repens with pollinaria on their proboscises, captured speci-
mens of B. vagans on plants of G . oblongifolia , and noted but did not capture or
identify other bumblebees visiting the flowers of G. tesselata in the same area. She
also reported halictid bees and syrphid flies on the flowers of G. repens , G. tesse-
lata , or G. oblongifolia , but none carried any pollinaria. Stevenson ( 1973 ), however,
observed the halictid, Augochlora pura (Say), removing pollinaria from G . pubes-
cens in North Carolina, and Homoya ( 1993 ) recorded Augochlorella aurata (Smith)
visiting flowers of this species in Indiana.
Ackerman ( 1975 ) described the pollination mechanism in G . oblongifolia , and
according to Kallunki ( 1981 ), the process is the same in G. tesselata and G. repens .
The flowers are slightly protandrous. The column in young flowers lies close to and
parallel with the lip, obstructing access to the stigma (Fig. 1.1d ). At this stage, the
elongate rostellum and viscidium in combination with the central groove of the
labellum form a narrow tube. This tube is large enough to admit the proboscis of a
visiting bee so long as it does not bear any pollinaria. The position of the column
thus prevents the bee from depositing pollen on the stigma of a young flower. A bee
with a naked proboscis probing for nectar at this stage ruptures the rostellum, con-
tacts the sticky viscidium with its proboscis (galea), and removes the pollinaria as it
withdraws from the flower (Fig. 1.3 ). In older flowers, the column and lip separate
(Ackerman 1975 ; Luer 1975 EXPOSINGTHESTIGMA&IG 1.1e ); the viscidium, if it
has not been removed, dries up (Ackerman 1975 ). Visiting bees carrying pollinaria
CANNOWEASILYDEPOSITPACKETSOFPOLLENORMASSULAEONTHEEXPOSEDSTIGMA!S
noted elsewhere, bees usually move upward on the inflorescence (e.g., Ackerman
1975 ; Corbet et al. 1981 ), and this behavior, in combination with the slight protandry
OFTHEmOWERSPROMOTESOUTCROSSINGALTHOUGHITDOESNOTOFCOURSEEXCLUDEGEITO-
nogamy among inflorescences in a clone or even among flowers within an inflores-
cence (see Spiranthes for a full discussion) (Kallunki 1981 ). Outcrossing is also
favored by sectile pollinia, which allow massulae from a single pollinium to be
deposited on a number of successively visited stigmas. Since all genes from a pollen
parent are present in each massula, pollen genotypes are more widely dispersed, and
the chances of a variety of genotypes being contributed to a single capsule may also
be increased (Freudenstein and Rasmussen 1997 ).
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