Exocarp Anatomy of Polygonum and Related Species from Shandong Province

The anatomical characters of the fruit exocarps of 20 species and 2 varieties of Polygonum and related species from Shandong Province were observed under light microscope.The results showed that the exocarp cells(in cross section)were square(isodia-metric),shortly rectangular,or elongated-rectangular,and aligned in parallel,resembling a palisade;the cell lumens were variable in shape and their sizes depending on cell wall thicke-ning,and may show branches or canals dichotomously or trichotomously or as dendritic ramifications at the outer limit anticlinal branching;the anticlinal walls were undulate or straight.Fruit exocarps were devided into three types based on the anticlinal wall patterns and cell lumen shapes,and they are,A.nearly narrow triangular cell lumen with dendritic ramifications and strongly flexuose anticlinal walls with numerous folds and gaps internally,e.g.Polygonum aviculare;B.nearly long and narrow cell lumen with dendritic ramifications,and were divided into two subtypes,B₁ the cell lumens irregular,and anticlinal walls strongly flexuose or waved,e.g.P.persicaria;B₂ the cell lumens regular,and anticlinal walls straight,e.g.P.bistorta;C.narrow cell lumen with dichotomous to quadrichotomous ramifications and straight anticlinal walls,e.g.Fallopia dumetorum.The anatomical characteristics have important systematic value to delimitation of the section and treatment of species in dispute within the family Polygonaceae.