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THERE HAS BEEN no published study of ovule development of an aneuploid apple. The degree of fruitfulness and meiotic behavior of an aneuploid is of interest to horticulturists, cytologists, and plant breeders in view of the probable allopolyploid origin of the species and the frequency of aneuploid seedlings in progeny of triploid varieties. This paper presents the results of a study of the reproductive phases of ovule development in the aneuploid apple selection New Jersey 4. The New Jersey 4 selection is an aneuploid seedling resulting from a cross of the triploid varieties Red Gravenstein X Close. There have been numerous studies (Shoemaker, 1926; Rybin, 1926; Howlett, 1931, 1932, 1938; Elssmann and von Veh, 1931; etc.) of some phase of development of the megaspore, female gametophyte, embryo and endosperm in apple but relativety few (Wanscher, 1939; Hough, 1947) have made a study of all phases and their interrelation. Maheshwari (1948) has thoroughly reviewed the literature oni development of the angiosperm embryo sac. MATERIALS AND METHODS.-New Jersey 4 was selected for study because of its many desirable horticultural and commercial characteristics, its unusual parentage and its failure to set consistently commercial crops of fruit in spite of profuse annual flowering. New Jersey 4 has a chromosome number of 44 ? 1. The diploid variety Jonathan, with 34 chromosomes, was selected to compare development of the megaspore, and female gametophyte, and of fertilization and development of the embryo and endo. sperm with similar developments in New Jersey 4. Daily collections were made from April 9 when the buds were in the "cluster bud" or "pre-pink" stage until 12 days after pollination. Periodic collections of New Jersey 4 fruit were made for 15 additional days. A crystal violet staining schedule similar to that described by Hancock (1942) was used. In this paper the descriptions given apply to both varieties studied uniless otherwise stated. DATA AND OBSERVATIONS.-A megaspore mother cell had differentiated in a small percentage of the ovules by April 7 when the flower buds were in the "cluster bud" or "pre-pink" stage of development. Typical prophase development followed early prophase, which persisted for some time. This was |
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