Chapter 1: The Characeae Plant

30
1.6 Figure and Table captions
Figure 1.1 Thallus of a characeae plant (Chara sp. r862). a) stem showing whorls of
branchlets, scale bar = 10 mm. b) reproductive organs, scale bar = 1 mm. c) Scanning
electron micrograph of an oospore of Chara sp. (r862), scale bar = 200 µm.
Figure 1.10 Tolypella glomerata (p798), a) whole plant showing basal axis, first nodal
complex with elongate simple branchlets, and numerous fertile branches. b) a single fertile
node with 8 branchlets in a whorl, each of which has a primary node with multicelluar rays
and gametangia. Oogonia and antheridia are clustered at the branchlet nodes, c) oogonium
prior to fertilisation with coronula intact, d) oogonium after fertilisation when the coronula
has fallen and the spiral cells have swollen.
Figure 1.11 Nitellopsis obtusa (t810). a) Axis of a female plant, with six branchlets in whorls
at the nodes, and elongate bract cells at the branchlet nodes. scale bar = 5 cm. b) Oogonium at
the branchlet node, subtended by bract cells, with a 5-celled coronula. Oogonia are usually
heavily calcified with the oospore developing within a calcareous lime-shell or gyrogonite. c)
Apex of a shoot showing absence of stipulodes and simple branchlets with elongate bract
cells. d) vegetative reproductive organ characteristic of Nitellopsis (after Fritsch 1948).
Figure 1.12 Morphology of Nitella. a) whole plant and b) corounula at the top of the
oogonium, c) terminal branchlet segments with central antheridium and bicellulate dactyls, d)
terminal branchlet segments with lateral oogonia and a central antheridium.
Figure 1.13 Diagrammatic representation of a transverse section through the lowest three
cells of a corticated branchlet of Chara. Cells are bounded by a cell wall, the cytoplasm is
bounded by the plasma membrane. The peripheral cytoplasm contains numerous discoid
chloroplasts (along with mitochondria, nuclei, golgi apparatus etc.) surrounding a central
tonoplast-bound vacuole. The branchlet structure consists of intermodal cells and nodal
complexes with cortical cells, bract cells, and gametangia arising at the nodes (after Fritsch
1948, Pickett-Heaps 1975 and Moestrup 1970).
Figure 1.14 Structures associated with spermatogenesis in characeae. a) spermatid of Nitella
with two flagellae, mitrochondria, nucleus and plastids (after Pickett-Heaps 1975 and
Moestrup 1970), b) part of the contents of an antheridium after removal of the shield cells c)
four of the eight shield cells.