Gametogenesis and Fertilization in Albugo

Abstract

1. A. Portulacae possesses a multinucleate oosphere which develops in a manner very similar to that of A. Bliti (Stevens1899), i. e., the nuclei all pass to the periplasm, dividing mitotically; and some of the daughter nuclei reenter the ooplasm, divide again, their products becoming the female nuclei, the plasmoderma being differentiated in the meantime. 2. Two mitoses occur in both oogenesis and spermatogenesis. 3. The nuclei return to the ooplasm after division much diminished in achromatic content. 4. The nuclear figure of the second mitosis is clearly distinguishable from the first by the diminished kinoplasm. 5. The antheridial tube is multinucleate. 6. The numerous antheridial nuclei fuse in pairs with the numerous oospheric nuclei, the number of fusion nuclei being usually larger than in A. Bliti. These fusion nuclei pass the winter without further change. 7. A coenocentrum somewhat less highly developed than that of A. Bliti is present. 8. The receptive papilla in A. Portulacae is larger than in the other known species. 9. A multinucleate oosphere develops in the same manner as in A. Bliti and A. Portulacae, and is then reduced to a uninucleate condition by disorganization of the supernumerary nuclei. 10. The nuclei pass to the periplasm, divide, and return to the ooplasm much diminished in achromatic content. 11. Two mitoses occur in oogenesis and spermatogenesis. 12. The nuclear figure of the second division may be distinguished from the first by a diminution of kinoplasm. 13. The antheridial tube conveys one or more nuclei into the oosphere where one fuses with the female nucleus. 14. Supernumerary male nuclei disorganize as do the supernumerary female nuclei. 15. The fusion nucleus undergoes repeated mitoses, and the winter oospore is consequently multinucleate. 16. the coenocentrum is very highly developed. It possesses an attraction for the primary oospheric nuclei and serves as a source of nourishment for the surviving female nucleus. 17. The oosphere is developed in a manner quite different from that seen in A. Bliti, A. Portulacae, and A. Tragopogonis. The periplasm and ooplasm are not differentiated until the second mitosis is completed. The nuclei, excepting one, eventually pass to the periplasm, which is then cut off by a wall. 18. One nucleus remains in the oosphere attached to the coenocentrum. 19. The coenocentrum attracts the nuclei very strongly, and later serves as a source of nourishment for the surviving female nucleus. 20. The antheridial tube occasionally contains two nuclei.