Abstract
It is remarkable that families like Apiaceae and Brassicaceae, characterised by uniform floral diagrams (i.e. stable positioning of floral organs relative to one another), show a great variability in initiation sequence of the floral organs. Within the subfamily Saniculoideae of the Apiaceae temporal overlaps in the initiation of the floral whorls ( Astrantia ), the formation of common stamen-sepal primordia ( Astrantia ), and segmentation in the formation of petals in pairs ( Sanicula ) occur. Reduction of the calyx and shortening of the plastochrons toward zero are trends found in the more advanced Apioideae ( Foeniculum , Levisticum ). Hydrocotyle , with its early sympetaly, resembles the Araliaceae more closely. Of interest is the fact that in Araliaceae the flower orientation is variable. Sometimes one sepal is opposite the subtending bract, a feature which becomes fixed in Cyphiaceae and Lobeliaceae of Campanulales, a sister group of Apiales.
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