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The journal of the Western Australian Herbarium

A new heterocarpidic fruit type for the Myrtaceae, with dehiscent and indehiscent loculi, in two genera from Western Australia

A form of heterocarpidy with dehiscent and indehiscent loculi present in the same fruit is described from species in two genera of Myrtaceae occurring in the south-west of Western Australia. This extreme development of heterocarpidy results in a very unusual fruit type, one that has not previously been described for the Myrtaceae. It is also apparently rare in the angiosperms, although smaller differences between carpels (mostly in their size and the number of seeds) are not uncommon. In Astus Trudgen & Rye and the Baeckea robusta F. Muell. complex, two types of ovary loculi develop, with one type dehiscent by a suture on the floral disc and the other type lower in the ovary and indehiscent. The occurrence of this heterocarpidic fruit type in two fairly different genera is considered to be a convergent development rather than indicating a particularly close relationship. The heterocarpidic fruit in these groups is described and illustrated, and its adaptive and taxonomic significance discussed.