Systematic Implications from Electron Microscopic Studies of Compositae Pollen-A Review

A discussion is presented of the pollen ultrastructure of 184 species from 11 Compositae tribes.For th d ee Astereae, Inuleae, Arctotideae, Mutisieae and Cichorieae the Although ultrastructural characters are given primary emphasis, light microscope observations, particularly the analyses of sectioned pollen walls, are also included.The results of our work are discussed in relation to taxonomy and phylogeny within the Compositae.1966] -SKVARLA & TURNER-COMPOSITAE POLLEN 2211926 and extending through 1945.These investigations did little to elucidate the internal features of the pollen wall, and it remained for Stix (1960), employing ultraviolet microscopy on sectioned pollen, to describe for the first time the internal morphology.Her descriptions, made from species representing all 13 tribes in the Compositae, showed a complexity of internal patterns which, in some instances, could be correlated with the external patterns shown by Wodehouse.She also showed that many of the pollen grains with superficially similar external surfaces were different internally.Stix recognized 42 "pollen types" in the Compositae, but no attempt was made to relate these types to specific tribal or phyletic lines.With the above studies as a base, we have undertaken electron microscopic investigations in the Compositae.We should emphasize at the outset that our work is done in concert with light microscopic observations on whole pollen mounts and on ly-sectioned pollen grains.In addition to obtaining higher resolution with the electron microscope, our approach contrasts with the ultraviolet work in that we have attempted to examine systematically a larger number of taxa before assigning pollen types.Below are listed the species of.Compositae we have examined with the electron microscope arranged by tribes following Hoffman (1897).