Biology Reference
In-Depth Information
Figure 1.
Nectaries in gymnosperms. Structurally bisexual organ complexes showing male
organs and sterile female organs with secretion drop at the micropylar orifice (
arrowheads
).
A,
Ephedra fragilis
, inflorescence with two upper female flowers, stamens of male flowers
still closed, ×9. B,
Welwitschia mirabilis
, flower with ovule in the centre, stamens still
closed, those of flower on the right side open, ×7.5. C, D,
Gnetum gnemon
. C, Two whorl
complexes, two male flowers open, each showing a stamen, other male flowers still in bud
stage, ×5. D, part of a whorl complex, a sterile female flower with secretion drop, ×12. (From
Endress, 1996, p. S119, Fig. 7; reprinted with permission of the University of Chicago Press,
Chicago.)
are located close to each other; they are visited at the same time and are re-
lated to the pollination of the plants bearing them.
In addition to insect pollination, wind pollination has been reported in
several
Ephedra
species (e.g., Bino & Meeuse, 1981; Niklas & Buchman,
1987), but it is now considered either impossible or negligible for
Gnetum
and
Welwitschia
(Kato et al., 1995; Wetschnig & Depisch, 1999), although
earlier articles suggested it.
The prevalence of entomophily in the extant Gnetales and its monophyly
as implied by recent molecular analyses (Rydin et al., 2002; Soltis et al.,
