10
C. den Hartog and J. Kuo
Amphibolis C. Agardh, Spec. Alg. 1 (1823) 474
Type species: Amphibolis zosteraefolia C. Agardh
(= A. antarctica (Labill.) Sonder et Ascherson.
According to Ducker et al. (1977, p. 68) the genus
Amphibolis was erected by C. Agardh (1823, p. 474)
as a green alga with two species, A. bicornis (1823,
p 474), and A. zosteraefolia, (1823, p. 475) from
New Holland. Later, Agardh (1824, p. 192) recognized A. zosteraefolia as synonymous with Ruppia
antarctica Labill., which was originally described
by Labillardi` ere (1806) as a flowering plant from the
shore of Western Australia. Ducker et al. (1977) selected A. zosteraefolia instead of A. bicornis as the
type of the Amphibolis, because, according to them,
the type specimen of A. zosteraefolia has the unique
grappling apparatus of which Agardh made the first
description.
This genus is fully restricted to the temperate
south and west coasts of Australia. It consists of two
species. A. antarctica is distributed from Victoria
and Tasmania in the east along the whole southern
and western coast of Australia north to Carnarvon.
The area of distribution of A. griffithii is more restricted; it occurs from Spencer Gulf in South Australia to the Geraldton area in Western Australia.
Posidoniaceae
Posidoniaceae Hutchinson, Fam. Fl. Pl. 2 (1934) 41;
nom. cons.
Typus: Posidonia K¨ onig
In earlier versions of the International Code of
Botanical Nomenclature the name of the family has
been ascribed to Lotsy (1911); he indeed used the
name but did not add a formal description of the
family.
Monoecious, perennial marine plants. Rhizome
creeping, herbaceous, monopodial, with branched
roots at the nodes; cortex with dark-colored secretory tannin cells. Scales covering the rhizome sheathlike, partly or completely amplexicaulous, scattered
with fine brown dots (tannin). Erect lateral shoots
ending in bundles of distichously arranged leaves.
Leaf-sheath amplexicaulous or subamplexicaulous,
biauriculate, ligulate. Leaf-blade linear with parallel
nerves. Sheath as well as blade with numerous dark
dots and stripes (tannin), the latter parallel with the
nerves. Inflorescence cymose, pedunculate. Flowers
hermaphrodite or masculine. Perianth absent. Stamens 3, sessile, consisting of a broad connective with
at each side an extrorsely dehiscent, bilocular theca.
Pollen confervoid. Gynoecium containing one orthotropous, parietal, pendulous ovule. Stigma irregularly lobed. Fruit with fleshy pericarp. Seed filled
completely by the embryo; embryo straight, consisting for the greater part of a large, fleshy hypocotyl
with an apical 4-polyphyllous plumula. Hypocotyl
with numerous tannin cells. Primary root present or
absent.
The family contains only the genus Posidonia, the
history of which goes back to the Cretaceous.
Posidonia K¨ onig in K¨ onig & Sims, Ann. Bot. 2
(1805) 95; nom. cons.
Type species: Posidonia caulini K¨ onig (= P. oceanica (L.) Delile)
The genus Posidonia has a rather remarkable pattern
of distribution; one species, P. oceanica, is completely restricted to the Mediterranean; the other
eight species of the genus occur in the waters of temperate Australia (Cambridge and Kuo, 1979; Kuo
and Cambridge, 1984). Although there is no need
to split the genus into sections or subgenera three
groups can be recognized. P. oceanica forms a group
in itself, because of the development of a significant primary root from the embryo. In the Australian species there is no development of a primary root at all. Among them two groups can be
distinguished.
P. australis, P. angustifolia, and P. sinuosa form
together the P. australis-group (Cambridge and
Kuo, 1979). These species are found in relatively
sheltered coastal waters where they can form extensive monospecific beds. They have thin, rather
flexible, short leaves, relatively large air lacunae and
rather few fibre bundles; their roots are rather fine
and much branched. Their leaf-sheaths are short, so
the meristems are not very deeply buried.
In contrast the five species of the P. ostenfeldiigroup (P. ostenfeldii, P. robertsoniae, P. denhartogii,
P. coriacea, and P. kirkmanii) grow in the open ocean
and in high energy coastal sublittoral habitats (Kuo
and Cambridge, 1984). They are characterized by
very long, thick, tough, leathery leaves, with narrow
air lacunae and an abundance of fibre bundles in the
subepidermal layer and in the mesophyll. The leafsheaths are very long, up to 25 cm, and the meristems are deeply buried in the substrate (20–30 cm);
the roots are very long and sparsely branched, showing wrinkled expanded thickenings up to 3 mm
thick.
C. den Hartog and J. Kuo
Amphibolis C. Agardh, Spec. Alg. 1 (1823) 474
Type species: Amphibolis zosteraefolia C. Agardh
(= A. antarctica (Labill.) Sonder et Ascherson.
According to Ducker et al. (1977, p. 68) the genus
Amphibolis was erected by C. Agardh (1823, p. 474)
as a green alga with two species, A. bicornis (1823,
p 474), and A. zosteraefolia, (1823, p. 475) from
New Holland. Later, Agardh (1824, p. 192) recognized A. zosteraefolia as synonymous with Ruppia
antarctica Labill., which was originally described
by Labillardi` ere (1806) as a flowering plant from the
shore of Western Australia. Ducker et al. (1977) selected A. zosteraefolia instead of A. bicornis as the
type of the Amphibolis, because, according to them,
the type specimen of A. zosteraefolia has the unique
grappling apparatus of which Agardh made the first
description.
This genus is fully restricted to the temperate
south and west coasts of Australia. It consists of two
species. A. antarctica is distributed from Victoria
and Tasmania in the east along the whole southern
and western coast of Australia north to Carnarvon.
The area of distribution of A. griffithii is more restricted; it occurs from Spencer Gulf in South Australia to the Geraldton area in Western Australia.
Posidoniaceae
Posidoniaceae Hutchinson, Fam. Fl. Pl. 2 (1934) 41;
nom. cons.
Typus: Posidonia K¨ onig
In earlier versions of the International Code of
Botanical Nomenclature the name of the family has
been ascribed to Lotsy (1911); he indeed used the
name but did not add a formal description of the
family.
Monoecious, perennial marine plants. Rhizome
creeping, herbaceous, monopodial, with branched
roots at the nodes; cortex with dark-colored secretory tannin cells. Scales covering the rhizome sheathlike, partly or completely amplexicaulous, scattered
with fine brown dots (tannin). Erect lateral shoots
ending in bundles of distichously arranged leaves.
Leaf-sheath amplexicaulous or subamplexicaulous,
biauriculate, ligulate. Leaf-blade linear with parallel
nerves. Sheath as well as blade with numerous dark
dots and stripes (tannin), the latter parallel with the
nerves. Inflorescence cymose, pedunculate. Flowers
hermaphrodite or masculine. Perianth absent. Stamens 3, sessile, consisting of a broad connective with
at each side an extrorsely dehiscent, bilocular theca.
Pollen confervoid. Gynoecium containing one orthotropous, parietal, pendulous ovule. Stigma irregularly lobed. Fruit with fleshy pericarp. Seed filled
completely by the embryo; embryo straight, consisting for the greater part of a large, fleshy hypocotyl
with an apical 4-polyphyllous plumula. Hypocotyl
with numerous tannin cells. Primary root present or
absent.
The family contains only the genus Posidonia, the
history of which goes back to the Cretaceous.
Posidonia K¨ onig in K¨ onig & Sims, Ann. Bot. 2
(1805) 95; nom. cons.
Type species: Posidonia caulini K¨ onig (= P. oceanica (L.) Delile)
The genus Posidonia has a rather remarkable pattern
of distribution; one species, P. oceanica, is completely restricted to the Mediterranean; the other
eight species of the genus occur in the waters of temperate Australia (Cambridge and Kuo, 1979; Kuo
and Cambridge, 1984). Although there is no need
to split the genus into sections or subgenera three
groups can be recognized. P. oceanica forms a group
in itself, because of the development of a significant primary root from the embryo. In the Australian species there is no development of a primary root at all. Among them two groups can be
distinguished.
P. australis, P. angustifolia, and P. sinuosa form
together the P. australis-group (Cambridge and
Kuo, 1979). These species are found in relatively
sheltered coastal waters where they can form extensive monospecific beds. They have thin, rather
flexible, short leaves, relatively large air lacunae and
rather few fibre bundles; their roots are rather fine
and much branched. Their leaf-sheaths are short, so
the meristems are not very deeply buried.
In contrast the five species of the P. ostenfeldiigroup (P. ostenfeldii, P. robertsoniae, P. denhartogii,
P. coriacea, and P. kirkmanii) grow in the open ocean
and in high energy coastal sublittoral habitats (Kuo
and Cambridge, 1984). They are characterized by
very long, thick, tough, leathery leaves, with narrow
air lacunae and an abundance of fibre bundles in the
subepidermal layer and in the mesophyll. The leafsheaths are very long, up to 25 cm, and the meristems are deeply buried in the substrate (20–30 cm);
the roots are very long and sparsely branched, showing wrinkled expanded thickenings up to 3 mm
thick.