nominal characters

Mr Fortuner connection modem fortuner at MATH.U-BORDEAUX.FR
Wed Apr 5 15:24:06 CDT 1995

Will the real nominal character stand up, please.

Eric Zurcher has a hard
time finding nominal characters. He proposes: "whether a particular structure
disarticulates or is persistent? But here we might quantify the force
required, or look for the presence of abscission layers."

I am no botanist,
but I don't think that this disarticulation thing can be replaced by force
required. There is a difference between forceful removal and presence of a
structure that exists for the sole purpose of making the leaves drop (the
abscission layer).

As for the presence of abscission layers, I disqualified
the presence/absence characters as such, but I never wanted to disqualify an
otherwise valid nominal character just because it can be replaced by a
presence/absence character. It seems to me that disarticulation is a good
example of a nominal character. Now, is it intraspecifically variable?

is an example of a nominal character in nematodes. The oviduct is made of
either two discs of four cells each or two rows of seven cells each. Here, the
number of cells that constitute the oviduct is an integer character (8 or 14),
but the arrangement of these cells is a nominal character: disc or tube. The
problem is that the fine structure of the oviduct has not been studied in most
species and we don't know if it is variable or not.

Characters are always
attached to a particular life stage. Sexual dimorphism, differences between
larval and adult stages, differences between dispersion-sedentary stages,
etc., cannot be used as example of variable nominal characters.

fortuner at

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