The genus Silphium (Asteraceae) is comprised of roughly 15 species, which are limited to eastern and central United States. Naturally occurring hybrids have not been documented, though they have been produced artificially. Two species, S. laciniatum , which is wide spread, and S.albiflorum , endemic to Texas, were utilized for this study. S. laciniatum has large leaves, some over two feet long each, which are very laciniate and lobed. S.albiflorum , which is theorized to have evolved from S. laciniatum , is smaller and also has laciniate leaves. The larger leaves overlap when they are folded to fit inside a plant press so analysis of entire leaves from typical herbarium specimens is impossible. This also prevents accurate measurements of leaf area, etc. and limits the amount of data gathered from an individual plant. Fractals are traditionally used to analyze geographic structures, such as coastlines. Defined as irregular fragmented shapes that exhibit intricate structure at all sizes so that details are reminiscent of the entire object, fractal measurements utilize different box sizes to measure a perimeter. A smaller box size provides a larger value for the perimeter. When fractals were used to measure small portions of leaves from S. laciniatum , S.albiflorum and putative hybrid populations, PCA analysis revealed delineation between the two species with the putative hybrid intermediate.

Key words: Fractal, leaf margin, Silphium (Asteraceae)