. Morphology of spermatophytes. [Part I. Gymnosperms]. Gymnosperms; Plant morphology. 100 MORPHOLOGY OP SPERMATOPHYTES as they descend. Upon reaching the base of the oospore the four nuclei arrange themselves in a plane and become ensheathed by fibers derived from the nuclear membrane. Two v?alls are then formed at right angles to each other and to the base of the spore, each nucleus thus being separated from the others, but freely exposed above to the general cytoplasm of the spore. Black- man ^'^ speaks of " each nucleus thus being at the bottom of a kind of shaft that opens above,"
. Morphology of spermatophytes. [Part I. Gymnosperms]. Gymnosperms; Plant morphology. 100 MORPHOLOGY OP SPERMATOPHYTES as they descend. Upon reaching the base of the oospore the four nuclei arrange themselves in a plane and become ensheathed by fibers derived from the nuclear membrane. Two v?alls are then formed at right angles to each other and to the base of the spore, each nucleus thus being separated from the others, but freely exposed above to the general cytoplasm of the spore. Black- man ^'^ speaks of " each nucleus thus being at the bottom of a kind of shaft that opens above," and the same author thinks that the ensheathing fibers, -which disappear at this time, have some intimate connection with the formation of the walls. In any event, the appearance of these first incomplete walls is quite apart from nuclear division, and the incomplete segmenta- tion of the cytoplasm presents a peculiarity which is paral- leled in the yolked eggs of certain animals. In fact, the method of receiving food sup- ply into the egg, the organ- ization of a small group of cells to develop the embryo, the setting aside of the great mass of the oospore as a nutri- tive supply, and the appear- ance of the peculiar walls about the basal nuclei seg- menting more or less the cyto- plasmic mass but not cutting it off, are facts which are all more suggestive of the embryogeny of certain animals than of other plants. Chamberlain observed one case in which the first and second segmentations of the fusion nucleus were accompanied by walls, a four-celled group thus appearing near the center of the oospore. According to our' observation, the walls which separate the four primitive nuclei, as mentioned above, do not appear until after the nuclei are in an advanced stage of division (Fig. 76, C). The spindles formed by the four basal nuclei are extremely broad and multipolar, but the later spindles are definitely bipolar. The basal nuclei divide simultaneously in a plane transverse.
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