| Abstract: | Studies on angiosperm phylogeny have taken the characters of pollen grains into
special account since good documentation on modern and fossil pollen morphology has become
available. The diversified pollen types within angiosperms obey a limited number of evolutionary
laws, and the successiformy and breviary are the most important morphological series.
The successiformy is a evolutionary succession of pollen types: tricolpate-pericolpate-periporate, which is linked to spherical pollen grains. The terminal form of successiformy, periporate
types, might have been derived through a different process. viz. the spiralization of apertures.
The breviary consists of a series of tricolpate-oblate to tricolporate-triporate pollen types,
which includes markedly oblate form and angular-aperturate pollen grains with a particularly
short polar axis.
The series of successiformy is found in taxa of the order Centrospermales and some taxa
of the Rosidae and Asteridae, while the breviary is widespread in many Rosidae and Amentiferae.
These morphological series have been otherwise proved in regard to the evolutionary direc-tions by the reliable fossil data. |
