SOME ASPECTS OF FLORAL VASCULAR SYSTEMS.

Abstract

A plea is made for a wider use of clearing techniques in studying floral vascular systems. Most investigators concern themselves with the primary vascular system of the flower. Comparisons should, therefore, be with the primary system of the stem in order to discover any evidence of intrinsic similarity between floral organs and leaves. The primary vascular systems of both can be interpreted as “open” or “closed”, but not in terms of leaf gaps and leaf traces as in dictyostelic ferns. Not only does this apply to flowers in which the stamens arise in centripetal succession (e.g. Ranunculaceae), but also to those in which they arise in centrifugal succession (e.g. Dilleniaceae, Tiliaceae, Paeoniaceae, in which branching vascular bundles supplying the stamens have previously been claimed as relics of an ancestral branch-like stamen). Stamens and leaves are, therefore, held to be homologous.