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The Gnetales (Gnetum, Ephedra, Welwitschia)
have been assumed to be the closest living relatives to flowering
plants.
To see these unusual gymnosperms click
here to be taken to a site at Southern Illinois University
| Evidence: |
| —
"double fertilization" (see Friedman papers on Links
page) |
| —reduced
female gametophyte |
| —leaves
with netted venation (see photos by clicking on SIU link above) |
| —cones
superficially resemble flowers (see photos by clicking on SIU
link above) |
| —
xylem with vessels |
| —rbcL
sequences place Gnetales are sister to angiosperms |
However, recent
molecular phylogenetic analyses place Gnetales with other conifers,
(Click here to see where Gnetales
fits in) leaving the closest relative of the flowering plants an
extinct lineage of gymnosperms that we have yet to discover in the
fossil record. For a discussion of the potential extinct candidates,
see class notes page 111.
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