and Siparunaceae) are probably defined by a multi-celled ovule archesporium and a crushed mesotesta. Within Laurales, 16 embryological characters are found to be diversified, including the number of microsporangia (four or two), mode of anther dehiscence (by slits or valves), the number of archesporial cells in an ovule (one, two or more), and so on. Their respective evolutions were traced on a phylogenetic tree generated from molecular and morphological data, supporting that Calycanthaceae represent the earliest branch and are sister to a clade comprising six remaining families with a valvate anther dehiscence as already suggested. However, because of a lack of sufficient data from each family of Laurales, embryological characters often have alternative possibilities with respect to where they have evolved. More extensive and/or intensive studies of individual families are needed to clarify their exact evolutionary relationships.
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