FLORAL ANATOMY OF IDIOSPERMUM AUSTRALIENSE (IDIOSPERMACEAE)

The floral anatomy of Idiospermum australiense (Diels) S. T. Blake is described from studies on relatively mature but unopened flower buds. The vascular system and general morphology of the flower is compared with that of Calycanthus and Chimonanthus (Calycanthaceae), especially with Calycanthus, the genus in which Diels originally placed Idiospermum. Inverted cortical bundles are present in both taxa but occur in different patterns. The tepals of Calycanthus are all 3-trace, whereas in Idiospermum only the upper tepals have three traces, the lower tepals having five to seven. All tepals of Calycanthus are spirally arranged; the lower tepals of Idiospermum are opposite or decussate in 1–3 pairs. The axial and recurrent bundle systems in Calycanthus are discrete except where the axial system turns downward, but in Idiospermum these systems, together with cortical bundles, are largely intermixed. The vascular supply to the carpel of Idiospermum, while possibly a modification of that of the carpels of Calycanthus, could also be interpreted as having an independent origin. Other differences and resemblances are described.