Status of Psilotum

Mushroom Research Lab DJR4 at psuvm.psu.edu
Thu Oct 27 12:03:28 EST 1994


I'm not about to do a literature search for anyone out there, but there seems t
o be simple problem with looking for SINGLE references with respect to the Psil
opsid question.  I have one from Science (Raubeson & Jansen, March 27 1992.  Vo
l 255:1697-1699.) which may not be the most recent or even completely relevant
or most accurate.  But at least it's something.  From the orientation of a 30-k
b region of chloroplast DNA, the authors conclude the following:  a)  3 lycopsi
ds share a Marchantia orientation; b)  all remaining vascular land plants studi
ed share a Nicotiana orientation; c)  "using Marchantia to polarize [an] invers
ion...  the Marchantia-moss-lycopsid condition [is] ancestral, whereas the rema
ining (nonlycopsid) vascular plants have the derived condition [not-inverted];
d)  ...Psilotum, sometimes considered primitive, is a derived member of the tra
cheophytes.  Nobody said that psilopsids are flowering plants, just as nobody s
aid that all vascular plants are flowering.  Numerous notes and references shou
ld prove useful, provided the final page of the report I mentioned is read.  Ch
eers!  Michael Nicholson.



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