Carpology and phermatology of Gomortega (Gomortegaceae): Systematic and evolutionary implications

Abstract

The anatomy and morphology of the fruits and seeds of Gomortega keule (Mol.) Baill., comprising a monotypic genus in the monogeneric family Gomortegaceae Reiche, have been studied in an effort to clarify its systematic position. The fruits are fleshy inferior cocnocarpous drupines, giving the appearance (due to the lateral concrescence of spirally arranged 2-6 carpels) of mostly 2-3-locular or rarely pseudomonomcrous syncarpous fruit. Seeds are flattened, exarillatc, abundantly albuminous with a small embryo, originate from hemianatropous crassinucellate, bitegmic ovules. The seed coat is endotestal- endotegmic; the endotesta, only testal layer preserved in the mature spermoderm, is of tracheotestal type, having peculiar numerous spiral or annular projections penetrating into the cell cavities. Evidence, mainly from seed anatomy and morphology, emphasizes phylogenetic unity of Gomortega having aberrant inferior fruits with Monimiaceae s.l. or more correctly, a group of the families Monimiaceae s. str., Amborellaceae, Hortoniaceae, Siparunaceae, and Atherospermataceae. Gomortegaceae especially have common roots with Atherospermataceae, sharing similar tracheotestal endotestal type of seed coats, albuminous seeds with small embryos, similar chromosome number, morphology of sieve-element plastids, palynomorphology, xylem anatomy, and distinctive staminodial appendages and valvular dehiscence of anthers. With the addition of more data on the fruit and seed anatomy and morphology of Atherospermataceae, the interrelationships of Gomortega and Atherospermataceae would be defined more precisely.