Status of Psilotum

sdigby at TIGGER.STCLOUD.MSUS.EDU sdigby at TIGGER.STCLOUD.MSUS.EDU
Thu Oct 20 13:43:16 EST 1994


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



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