SHOOT AND FLORAL DEVELOPMENT IN CALLA-PALUSTRIS (ARACEAE, CALLOIDEAE)

Calla palustris shows annual production of one or two inflorescences on each ephemeral seasonal shoot. Shoots are sympodial; the terminal inflorescences are produced in the summer of the year before the mostly perfect flowers open. Overwintering terminal buds show limited preformation of foliage leaves on renewal shoots; most leaves are neoformed. The spadix produces a series of prominent flower primordia in up to eight irregular orthostichies. Each primordium develops no perianth but a series of indistinctly trimerous stamen initials in centripetal order. The gynoecium originates as a single dorsiventrally asymmetric collar-like outgrowth that becomes ovate and encloses the series of basal anatropous ovules, showing no evidence of a pseudomonomerous condition either in development or vasculature. Floral variation within a spadix is considerable, distal flowers are usually wholly male, basal flowers show reduced stamen number, but no strictly female flowers are produced. Vascular traces to the floral appendages are derived from an anastomosing system that obscures any uniform pattern. Morphogenetic considerations describe the vascular system better than any reference to imaginary evolutionary antecedents.