Building on two centuries of history, we advocate an expanded and maximally informative format for floral formulae to describe angiosperm flowers in formal taxonomic descriptions. Using standard typeface and Unicode character codes, the format can summarise a wide range of features, including: acropetal sequence of organ initiation, number and symmetry of each whorl of floral organs (bracts, sepals, petals [or tepals], androecium, gynoecium, ovules), position of the organs relative to each other, partial and/or complete fusion of organs, resupination, organ loss and suppression, and deviations from standard bisexuality. We use several complex flowers to demonstrate our view that all known flower morphs can be accurately represented by the updated format, and show how use of floral formulae can outline some unanswered questions regarding the floral organisation of the model organism Arabidopsis. Possible uses of floral formulae extend beyond static description of mature morphology into the comparative realm. When combined with phylogenies, they help to elucidate generalised groundplans, plesiomorphic architecture, and the location and polarity of particular character-state transitions. They can usefully be applied within as well as between species, to compare wildtype versus mutant morphs and different ontogenetic stages. Perhaps their greatest strengths are that they (1) require only a universally available typescript, and (2) bring a comprehensive uniformity to the description of flowers, acting as a checklist of features to be examined. We recommend that floral formulae become a routine component of diagnoses in protologues and other formal taxonomic (re)descriptions, functioning as a logical phenotypic counterpart to the DNA barcode.
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Document Type: Research Article
Jodrell Laboratory, Royal Botanic Gardens, Kew, Richmond, Surrey, TW9 3DS, U.K.
Jodrell Laboratory, Royal Botanic Gardens, Kew, Richmond, Surrey, TW9 3DS, U.K.; Department of Geography, Environmental and Earth Sciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, U.K.
Publication date: 01 February 2010
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