The Essex Naturalist
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example been used to describe the variable and environmentally influenced
morphology of the moss Fissidens bryoides sensu lato.
In Chara vulgaris, the bracteoles and adaxial bract cells are often very
extensive and may be up to 6x the length of the oogonium. A further character
involves the degree of development of the spine cells. These may be
undeveloped ("rudimentary"), globular or cylindrical, and the latter may be
spreading or they may be recurved. Additionally the spines may be persistent or
deciduous. Furthermore, sinking the formerly separate species Chara contraria
and its variety hispidula, as varieties of C. vulgaris (Moore et al, 1986) on the
grounds that the relative prominence of the primary and secondary cortical rows
is a variable character, introduces further potential combinations. Sometimes
the branchlets are wholly ecorticate, adding another character to the set. In the
case of the stipulodes, they may be well, or less well developed, and the upper
and lower series equal in size, or the upper ones may be larger. Finally, the
branchlets may be more or less equal in length to the internodes, or much
shorter than the internodes, and may be spreading or incurved. In order to be
able to record these various forms, I propose therefore, the following score chart
and associated letter codes, and that we either score a set of codes for each plant
or cover all the potential characters in a word description.
Chara vilgaris character expression codes:
Long bracteoles/adaxial bract cells (L), spines undeveloped (U), globular (G),
cylindrical (C), spreading (S), recurved (R), persistent (P), deciduous (D),
primary rows prominent (1), secondary rows prominent (2), rows equal (3),
branchlets ecorticate (E), stipulodes poorly (SP)/well developed (SW), upper
and lower stipulodes equal in size (SE), upper stipulodes distinctly larger (UL),
branchlets about equal to internodes (BE), or much shorter (BS), and spreading
(BG) or incurved (BI).
Only by building up a dataset of the various combinations will we be able to sort
out whether any of these really are correlated with each other or whether they are
independent variables. In the case of the varieties vulgaris, longibracteata and
papillata for example, the three forms appear in some cases to replace each other in
sequence in the same pond as the seasons progress. What we are still uncertain of,
is whether these are due to the sequential germination of three types of genetically
different oospore, or whether the same genotype is responding morphologically to
a subtle temporal change in the habitat. Similarly, where variation occurs in other
charophyte taxa, it would be useful to record a word description for each find, and
follow up any morphological changes throughout the year.
The Essex records
Although most of the likely national and local herbaria have been examined for
Essex specimens, largely by Jennifer Moore during the preparation of the
Charophyte Atlas (Moore 6k Green, 1983), the numerous additional field records
have accumulated on a serendipitous basis, rather than from a systematic survey.