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A Morphological Study of Diospyros Virginiana

1911; University of Chicago Press; Volume: 52; Issue: 1 Linguagem: Inglês

10.1086/330571

1940-1205

Stella M. Hague,

Plant and animal studies

1. The flowers are developed on shoots of the same season's growth. The floral cycles appear in the following order: a pair of bracts, the calyx, the corolla and stamens, and lastly the pistil. 2. The ovule is anatropous and has two integuments. A single mother cell is formed beneath the outermost layer of the nucellus, from which four megaspores develop, the chalazal one becoming the embryo sac. 3. The embryo sac at the eight-celled stage is small, somewhat pointed at the micropylar end, and rests upon a stalklike portion of the nucellus. A tapetal layer of cells from the inner integument completely surrounds it. The egg apparatus in this stage is not conspicuous; the polars are large and striking in appearance; the antipodals are found with so much difficulty that it is probable that one or more of the cells is often lacking. 4. The studies of pollination and fertilization are not complete. Little evidence of pollination has been found and none of fertilization. The production of seedless fruit is probably involved in the problem of pollination. 5. After the flowers fall, the whole ovule increases rapidly in size. The egg enlarges and becomes filled with densely staining globules. The primary endosperm nucleus divides early and the endosperm fills the sac, and then crowds the inner integument quite up to the dense outer one. 6. The embryo is late in appearing. The earliest stage identified was a three-celled one in the extreme micropylar region. The tendency to variation seen in many of the stages is shown here in the two types found, the freak embryos and the case of polyembryony. 7. Pollen mother cells were found on a tree a week before the older flowers opened. The mother cells are large and the whole mass is surrounded by a single tapetal layer. The spindle in the tetrad formation is small, the chromosomes being 30 or more. The pollen grains show some difference in size, and frequently only one nucleus could be distinguished.