FLORAL BUNDLE FUSION AND VASCULAR CONSERVATISM

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Abstract
Summary: Critiques are presented of the three main precepts of vascular conservatism, viz.: (1) extent of fusion of bundles denotes degree of evolutionary advancement; (2) 'vestigial traces' indicate organs that have disappeared because vascular patterns lag behind in evolution; and (3) orientation of bundles demonstrates homologies. Precepts (2) and (3) can be controverted to a large extent by existing reports in the literature. Precept (1) is herewith tested by an analysis of the level and manner of origin of the dorsal carpellary bundles of four species of Syzygium s.l. (Myrtaceae). These features are very variable in an individual plant and even in a single flower. Consequently, the extent of union between bundles, contrary to widespread belief, is not necessarily a reliable indicator of phyletic status of an organ or taxon. There is no a priori reason to expect hypotheses based upon conservatism to apply to all situations. The only ultimate test is correlation with other lines of evidence.