Abstract: The experiment was conducted by means of routine paraffin-embedded sectioning technique to offer some information for embryology and taxonomy of Plantaginaceae. The results were as follows：Mature megagametophyte was of Polygonum-type with 7 cells and 7 nuclei. Fertilization resulted in zygote and primary endosperm nucleus. Development of endosperm was of Cellular-type，as the first division of primary endosperm nucleus separated a micropylar and chalazal chamber. The micropylar chamber turned into 2- or 4-celled by one or two vertical division at right angle to each other，then a transverse division in each cell formed 4 or 8 cells arranged in two tiers. Each cell of the micropylar tier （2 or 4 cells） developed into a one-nucleated micropylar haustorium，and the other 2 or 4 cells of the lower tier gave rise to a endosperm proper surrounding embryo. Meanwhile the chalazal chamber developed into a binucleate haustorium by mitosis without division of cytoplasm. Haustorium absorbed and transformed nutrition from integument and chalaza to endosperm proper. The embryogeny conformed to Onagrad type，and mature seed developed from proembryo-heart–torpedo-cotyledon stage. Integument tapetum was well-developed. Relative nuclear DNA content of nuclei was measured by flow cytometry which showed that embryo was diploid and endosperm was triploid.

Key words: Plantago major L., embryo, endosperm, endosperm haustorium, flow cytometry, DNA ploidy, integument tapetum