Chapter 1: The Characeae Plant

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of inflated branchlets develop, clustered towards the top of the axis. The inflated parts of the
plant are the branchlet cells, and often only the second (or penultimate) cell of the branchlet
(Fig. 1.9b). In comparison the axis cells are narrow and thick-walled. The plants are
monoecious and the oogonia and antheridia are clustered at the bases of whorls and at the
branchlet nodes (Fig. 1.9c, d). Many specimens of Lamprothamnium have inflated sterile
branchlets, but L. inflatum has also inflated fertile branchlets. In common with other species
of Lamprothamnium it tolerates fluctuations in the salinity of its medium, and probably
doesn’t thrive in fresh water. Its natural distribution is in brackish to saline temporary
wetlands in the south of Western Australia, South Australia and Kangaroo Island.
1.2.5 Species of Tolypella
The genus Tolypella (Fig. 1.10) appears to be restricted to latitudes greater than c. 40° in both
the Northern and Southern Hemispheres (Wood 1965). The genus is characterised by its
relatively disorganised thallus, with large numbers of sterile and fertile branchlets, branches
and reproductive organs arising from the nodal complexes. Plants usually consist of a long
protonema or primary axis cell from which a series of complex nodes arise, each with many
simple sterile branchlets, branches and reproductive organs arranged in a disorganised
fashion (Fig. 1.10a). The structure of the branchlets is different from that of members of
Chara, Lamprothamnium or Nitella, consisting of a primary branchlet cell, a nodal complex
that produces the continuation of the primary ray, a number of secondary rays and
reproductive organs (Fig. 1.10b, c). The antheridia and oogonia are often stalked (stipitate)
and the oogonia have 10 coronula cells (Fig. 1.10d). In some of the species of Tolypella the
coronula is deciduous (i.e. falls off at maturity) and the spiral cells become swollen (Fig.
1.10e). Some species produce gyrogonites (lime-shells) around the oospores. The oospores
are terete in cross-section (c.f. Nitella in which the oospores are flattened in cross-section),
and often flanged on the striae.
The common name for some species of Tolypella is the ‘birds nest’ or ‘tassel’ stonewort,
eflecting the highly divided and disorganised nature of the thallus. Many species can tolerate
salinity to varying degrees (Winter et al. 1996), but they do not grow in strictly marine
systems. Although species of Tolypella occur in permanent lakes in North America, there
appears to be a higher diversity of species in temporary systems, requiring disturbance or
drying of their habitat for the maintenance of populations (Stewart and Church 1992).