OVULE DEVELOPMENT IN ORNITHOGALUM CAUDATUM (LILIACEAE) WITH A REVIEW OF SELECTED PAPERS ON ANGIOSPERM REPRODUCTION

SUMMARY Archesporial cell differentiation begins when ovules are four or five cells long. One parietal cell separates the archespore and nucellar epidermis. The parietal cell divides once anticlinally and its daughter cells divide once or twice periclinally resulting in four or six parietal cells. Archespore cytoplasm contains numerous small vacuoles and numerous circular, rod‐shaped bodies which stain for protein. RN A content is high. Archesporial cells increase two‐ or threefold in size and produce a megaspore mother cell which is circular in cross‐section and elliptical in longisection. Vacuoles seem to shrink slightly during the archespore/megaspore mother cell transition. Meiosis produces four megaspores separated from each other and from the nucellus by walls which stain intensely with basic fuchsin but do not fluoresce with Aniline blue. The chalazalmost megaspore typically becomes the functional megaspore while the others degenerate. Carbohydrates accumulate in the functional megaspore during the meiotic/mitotic interphase, and by metaphase, organelles, including amyloplasts, are in a perinuclear arrangement.