Comparative seed morphology of Boronia and related genera (Boroniinae: Rutaceae) and its systematic implications

Comparative seed morphology of Boronia Sm., Boronella Baill., Neobyrnesia J. A. Armstr. and Zieria Sm., 31 taxa in total, in Rutaceae is studied. The seeds are ventrally ellipsoid to ovoid (0.934.42 X 0.502.31 X 0.952.70 mm). Colour is brown to black. An elaiosome which is related to myrmechocory was observed in Boronella, Boronia, Neobyrnesia and Zieria. Six testa surface pattern types are identified: Type I (Boronia sect. Boronia) smooth, and cells not barely discernable; Type II (Boronella) smooth and cells more or less rectangular and often cells elongated; Type III (Boronia sects. Boronia, Cyanothamnus, Imbricatae and Valvatae, Neobyrnesia) colliculate with four subtypes by presence, absence of ridges or ridge characters; Type IV (Boronia sect. Alatae) digit form; Type V (Boronia sect. Algidae) alveolate; Type VI (Zieria) ridged, the interridge area formed by both cells that form the ridges and cells that do not form the ridges. Seed morphology, especially testa surface patterns, was partially congruent with the current classification of Boronia, with most sections having apomorphies, and provided additional support for the placement of Boronella near Boronia sect. Boronia. Hilum (surrounded by labiose margin or not) and elaiosome shape also offer useful diagnostic characters for Boronia at infrageneric levels. Neobyrnesia and Zieria both had unique testa surface patterns. The seed morphological data contribute to our understanding of systematic relationship in the subtribe Boroniinae.