 Gymnosperms (Gymnospermae) are a group of seed-bearing plants which bear seeds on cone-like structures rather than inside fruit. The term gymnosperm comes from the Greek word gumnospermos, translated literally "naked seed". The name points out that the seeds are not formed in ovules or found inside fruit, as they are in angiosperms, but are found naked on the scales of a cone or similar structure.
The production of seeds distinguishes the gymnosperms (along with the angiosperms) from other members of the vascular plants. Thus together they are called seed plants (Spermatophyta).
Gymnosperms are heterosporous, producing microspores that develop into pollen grains and megaspores that are retained in an ovule. After fertilization (joining of the micro- and megaspore), the resulting embryo, along with other cells comprising the ovule, develops into a seed. The seed is a sporophyte resting stage.
In early classification schemes, the gymnosperms (Gymnospermae) "naked seed" plants were regarded as a "natural" group. However, certain fossil discoveries suggest that the angiosperms evolved from a gymnosperm ancestor, which would make the gymnosperms a paraphyletic group if all extinct taxa are included. Modern cladistics only accepts taxa that are monophyletic, traceable to a common ancestor and inclusive of all descendants of that common ancestor. |
