72
J. Kuo and C. den Hartog
A
B
C
D
H
G
F
E
I
J
K
L
Fig. 12. Morphology, anatomy and ultrastructure of male flowers. A. Halophila ovalis. A maturing male flower with an extending pedicel
(Pe) and a pigmented, swelling tepal (T). Scale = 4 mm. B. Halophila beccarii. The tepals (T) open to release pollen grains (P) in chains.
Scale = 2 mm (Courtesy of Dr. B. Japar Sidik). C, D. Heterozostera nigricaulis. The monoecious flower has male and female flowers
arranged in two rows; in each row a male flower with two thecae (T) alternates with a female with an ovary (O) and a long stigma (St). A
small retinacula (R) occurs between two thecae. Scales C = 2 mm, D = 400 µm. E. Syringodium isoetifolium. Two anthers (A) form at
the same level. Scale = 5 mm. F. Halodule uninervis. Two anthers (A) form at the different levels. Scale = 2 mm. G. Thalassodendron
pachyrhizum. Each male flower (F) has two different developmental stages. Scale = 5 µm. H–L. Posidonia australis. Mature stamens
(S) slit longitudinally to release a mass of thread like pollen (P), rich in starch. Each pollen has two vegetative nuclei (VN) and a sperm
nucleus (SN). Scales H = 5 mm, I, J = 55 µm, K = 4 µm, L = 6 µm.
are small in Heterozostera (Fig. 12C) and Zostera
subgenus Zosterella, and absent in Zostera subgenus
Zostera. At anthesis, anthers slit longitudinally to
release filamentous pollen. After anthesis, anthers
detach from the spadix in monoecious flowers, but
the entire male flowers detach from dioecious plants,
while stigmata break off from styles in all species. It
should be noted that the reproductive arrangement
in the Zosteraceae is unique among seagrasses and
the angiosperms. As there is no similar flowering
pattern occurring in the terrestrial flowering plants,
it may be suggested that the Zosteraceae have a very
ancient marine/aquatic origin.
4. Posidoniaceae
In the Posidoniaceae, inflorescences are supported
by long peduncles; they are racemose with leafy
bracts; the ultimate units are spike-like, with several to 30 apparently naked flowers. The flowers are
J. Kuo and C. den Hartog
A
B
C
D
H
G
F
E
I
J
K
L
Fig. 12. Morphology, anatomy and ultrastructure of male flowers. A. Halophila ovalis. A maturing male flower with an extending pedicel
(Pe) and a pigmented, swelling tepal (T). Scale = 4 mm. B. Halophila beccarii. The tepals (T) open to release pollen grains (P) in chains.
Scale = 2 mm (Courtesy of Dr. B. Japar Sidik). C, D. Heterozostera nigricaulis. The monoecious flower has male and female flowers
arranged in two rows; in each row a male flower with two thecae (T) alternates with a female with an ovary (O) and a long stigma (St). A
small retinacula (R) occurs between two thecae. Scales C = 2 mm, D = 400 µm. E. Syringodium isoetifolium. Two anthers (A) form at
the same level. Scale = 5 mm. F. Halodule uninervis. Two anthers (A) form at the different levels. Scale = 2 mm. G. Thalassodendron
pachyrhizum. Each male flower (F) has two different developmental stages. Scale = 5 µm. H–L. Posidonia australis. Mature stamens
(S) slit longitudinally to release a mass of thread like pollen (P), rich in starch. Each pollen has two vegetative nuclei (VN) and a sperm
nucleus (SN). Scales H = 5 mm, I, J = 55 µm, K = 4 µm, L = 6 µm.
are small in Heterozostera (Fig. 12C) and Zostera
subgenus Zosterella, and absent in Zostera subgenus
Zostera. At anthesis, anthers slit longitudinally to
release filamentous pollen. After anthesis, anthers
detach from the spadix in monoecious flowers, but
the entire male flowers detach from dioecious plants,
while stigmata break off from styles in all species. It
should be noted that the reproductive arrangement
in the Zosteraceae is unique among seagrasses and
the angiosperms. As there is no similar flowering
pattern occurring in the terrestrial flowering plants,
it may be suggested that the Zosteraceae have a very
ancient marine/aquatic origin.
4. Posidoniaceae
In the Posidoniaceae, inflorescences are supported
by long peduncles; they are racemose with leafy
bracts; the ultimate units are spike-like, with several to 30 apparently naked flowers. The flowers are