Biology Reference
In-Depth Information
Fig. 8.2
Arethusa bulbosa
. (
a
) Flower, oblique view, scale bar = 5 mm; (
b
) Column, ventral view,
scale bar = 5 mm; (
c
) Close up of anther (an) and stigma (sg), scale bar = 1 mm
The flowers of
A. bulbosa
are relatively large and usually solitary and terminal
on scapes of variable length (Table
8.1
). Commonly rose-purple, they range from
magenta to white (Luer
1975
; Case
1987
; Yannetti
2003
). All three sepals are erect,
whereas the petals are positioned with the lip to form a loose tube around the col-
umn (Fig.
8.2a
). The lip is obovate to oblong with two indistinct lateral lobes and a
large, downcurved middle lobe. The latter has a notched apex, crenulate to erose
lateral margins, and deep purple veining or blotching on an otherwise white or pink-
ish-white ventral surface. This surface also bears ultraviolet absorbing crests of yel-
low lamellae, which become fleshy processes toward the apex (Luer
1975
). The
column is pink, flattened, and arched with lateral wings and a distally erose margin
(Fig.
8.2a, b
) (Luer
1975
; Case
1987
). Positioned below the apex, the incumbent
anther (Fig.
8.2b, c
) produces two pairs of soft and mealy, weakly sectile, yellow-
green pollinia (Luer
1975
; Hesse et al.
1989
; Dressler
1993
). The massulae are
irregularly shaped and comprised of tetrads (Hesse et al.
1989
). The stigma is emer-
gent and proximal to the anther (Fig.
8.2b, c
) (Sheviak and Catling
2002a
). A vis-
cidium is absent (Stoutamire
1971
).
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