Evolution of Leaves: Microphylls and Megaphylls
The "Enation theory" of microphyll development posits that small outgrowth, or enations, developed from the side of early axes (such as those found in the Zosterophylls). Outgrowths of the protostele later emerged towards the enations (as in Asteroxylon), and eventually continued to grow fully into the leaf to form the mid-vein (such as in Baragwanathia). The fossil record appears to display these traits in this order, but this may be a coincidence, as the record is very incomplete: microphylls may have originated by the reduction of a telome branch.
Read more about this topic: Microphyll
Famous quotes containing the words evolution of and/or evolution:
“Historians will have to face the fact that natural selection determined the evolution of cultures in the same manner as it did that of species.”
—Konrad Lorenz (1903–1989)
“The more specific idea of evolution now reached is—a change from an indefinite, incoherent homogeneity to a definite, coherent heterogeneity, accompanying the dissipation of motion and integration of matter.”
—Herbert Spencer (1820–1903)