Leaf Venation Patterns / Annonaceae

Leaves are the most common and visible organs of living plants, herbarium specimens, and fossil remains and their general patterns of venation are easily recognized and seemingly quite distinct. E.J.H. Corner (1968) wrote that, „Patterns of veins differ greatly according to the kinds of plants and, if they were properly understood and could be described accurately, they would be found as characteristic of plant species as fingerprints of human beings.“ This ideal is a long way from being realized and may not prove to be feasible. The venation of individual specimens, particularly fossil ones, has long been used for species identification. However, in order to determine how reliable venation patterns are for identifying plants the different kinds of existing patterns should be worked out and their distribution among the angiosperms be determined. As a means for working out the existing kinds of venation patterns one can use either a developmental approach or an evolutionary one. In the developmental approach the venation patterns are considered to be products of stages of individual maturation whereas in the evolutionary approach they are considered to represent phases of taxon development. The developmental approach is here for describing the venation patterns of the Annonaceae.