Some botanists view Psilotum nudum as a living fossil, very similar in structure to the earliest vascular plants. Figure A shows the vascular cylinder of the Psilotum nudumsporophyte. B is a preserved ...

II. COMPARISON of these four fossil species from Rhynie with other fossils already known from the early Devonian period shows that a very homogeneous flora existed at that time, consisting chiefly of ...