Biology Reference
In-Depth Information
Table 6.3 Data on Tipularia (Catling and Sheviak 2002 )
Character
Tipularia discolor
Plant height (cm)
10-65
Raceme length (cm)
8-28
Flower number
(5-) 10-55
Dorsal sepal (mm)
5-8 × 1.5-2.8
Lateral sepals (mm)
5-8 × 1.5-2.8
Lateral petals (mm)
4-7 × 1-1.8
Lip (mm)
5-8 × 2.5-3
Spur length (mm)
10-23
Column (mm)
2.5-4
Tipularia discolor (Pursh) Nuttall (Crane-Fly Orchid)
Distribution and Habitat
T. discolor is a common wintergreen orchid in deciduous and coniferous forests
throughout most of eastern North America. It is found from southern Missouri east
to Massachusetts and south to Texas and Florida (Whigham and McWethy 1980 ;
Brown 1998 ; Catling and Sheviak 2002 ).
Floral Morphology
A highly variable number of small, greenish-yellow to greenish-purple, resupinate
flowers are loosely arranged on a slender raceme (Table 6.3 ) (Luer 1975 ). Flower
symmetry is unusual with the column directed either to the right or to the left of the
nectary opening. Both left- and right-handed flowers occur on each raceme (Stoutamire
1978 ). The sepals and petals also have an altered and irregular orientation, with one
or more often asymmetrically positioned in the perianth (Fig. 6.3a, b ) (Luer 1975 ;
Stoutamire 1978 ). It is the only North American orchid that shows such modified
symmetry. Both Asian species have bilaterally symmetrical flowers, and Stoutamire
( 1978 ) considered this the ancestral condition. The lip is trilobed with small, rounded,
lateral lobes and a narrow central lobe, slightly spreading at the tip (Fig. 6.3b ) (Luer
1975 ). It is extended basally into a long, narrow nectar spur (Fig. 6.3a ; Table 6.3 )
(Luer 1975 ). A slightly curved, 2.5-4 mm long column bears one terminal, incum-
bent anther containing two pairs of hard, superposed, yellow pollinia (Fig. 6.3c, d ).
All four pollinia are attached to a single 1 mm long, elastic stalk with a basal vis-
cidium, the latter enclosed in a bifid flap of the rostellum (Luer 1975 ; Catling and
Catling 1991 ; Dressler 1993 ; Catling and Sheviak 2002 ). The stalk in Tipularia is a
unique type of unrecurved stipe derived through elongation and detachment of the
rostellum (Freudenstein 1994a ). The stigma is sticky, entire, and located behind the
anther (Whigham and McWethy 1980 ). The flowers produce a perceptible, nocturnal
fragrance (Stoutamire 1978 ), which Schnell ( 1997 , p. 438) described as “a very faint
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