Abstract
Isolated ovules from the Upper Triassic of Zimbabwe were observed using three complementary approaches: light microscopy and, for the first time, scanning electron microscopy and transmission electron microscopy. Complete ovules showed a curved bifid micropylar tube. Three envelopes were present: integument, nucellus, and megaspore. The integument appeared resiniferous. The nucellus was made up of bulging cells around the pollen chamber, which contained bisaccate pollen grains. The ultrastructure of the nucellus revealed a lamellar organization in their microsinuosities. The megaspore membrane was made up of agglomerate rounded bodies more or less closely arranged and surrounded by two layers. The material may be attributed to Umkomasiaceae. A comparison with ovules of different related groups (seed ferns, Caytoniales, Ginkgoales, Nilssoniales, and Coniferales) was made. The Umkomasiales are considered to be a more primitive group than the Pteridospermales with regard to integument and nucellus.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
