Status of Psilotum
MELAN at duq3.cc.duq.edu
Tue Oct 25 15:20:56 EST 1994
sdigby at TIGGER.STCLOUD.MSUS.EDU wrote:
: In article <amacdona.39 at cs-acad-lan.Lakeheadu.Ca>, amacdona at cs-acad-lan.Lakeheadu.Ca (DR A MACDONALD BIOLOGY) writes:
: >What is the present state of evidence to support the views of Bierhorst that
: >the Psilotophyta are primitive leptosporangiate ferns close to the
: >Stromatopteridaceae? I am not happy in class talking about this group as
: >Rhynia-like etc....In fact I don't.
: >amacdona at cs_acad_lan.lakeheadu.ca (Alastair Macdonald)
: Very simply - you are right about feeling uncomfortable. Bierhorst and Don
: Kaplan had an ongoing rather violent disagreement on the subject. Psilotum is
: only a fern using Bierhorst's view of the world and I think he was pushing it.
: In any event, chloroplast DNA work has shown that Psilotum is close to the
: flowering plants - in other words it is probably secondarily "primitive" in
: morphology. Cannot of-hand recall the actual reference on chloroplast DNA -
: if anyone does have the reference, can you send it to me.
: Stephanie Digby, St. Cloud State, MN
Psilotum is close to flowering plants???? I think that the
chloroplast DNA work showed that Psilotum is in fact truly primitive and
is neither a derived fern nor certainly not a flowering plant. The work was
done by Diana Stein, David Conant and others and was published about two
years ago in Science with a related paper in PNAS. Sorry that I don't
have the actual reference in hand to give the citation.
Melissa Melan (melan at duq3.cc.duq.edu)
Department of Biological Sciences
Pittsburgh, PA 15282
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