. Morphology of gymnosperms. Gymnosperms; Plant morphology. 384 MORPHOLOGY OF GYMNOSPERMS all. In no case does it divide until the inner daughter cell has com- pleted its division (fig. 431). This situation is so general that a row of three cells occupying the position of a tetrad hardly deserves atten- tion. The chromosomes have been counted in Ephedra (18, 23) and in Gnetum (25), and in both the numbers are 12 and 24, conform-. FiGS. 431, 432.—Ephedra irifurca: fig. 431, row of four megaspores, the lowest beginning to enlarge; fig. 432, simultaneous free nuclear division to form the 64- nucl
. Morphology of gymnosperms. Gymnosperms; Plant morphology. 384 MORPHOLOGY OF GYMNOSPERMS all. In no case does it divide until the inner daughter cell has com- pleted its division (fig. 431). This situation is so general that a row of three cells occupying the position of a tetrad hardly deserves atten- tion. The chromosomes have been counted in Ephedra (18, 23) and in Gnetum (25), and in both the numbers are 12 and 24, conform-. FiGS. 431, 432.—Ephedra irifurca: fig. 431, row of four megaspores, the lowest beginning to enlarge; fig. 432, simultaneous free nuclear division to form the 64- nucleate stage of the female gametophyte; Xsoo.—^After Land (18). ing to the remarkably imiform condition of gymnosperms in this regard; although Jaccaed (14) reports 8 and 16 for Ephedra hel- vetica. If several tetrads are produced in a single ovule, several megaspores may begin to function, and in the case of Gnetum several contiguous embryo sacs with free nuclei may be formed. 3. The gametophytes THE FEMALE GAMETOPHYTE The development of the female gametophyte is so strikingly differ- ent in the three genera that they must be described separately. The course of development in Ephedra was first outlined by Stras- BURGER (3), and it conforms to that described for conifers, with free nuclear division, vacuolation accompanied by parietal placing, for-. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Coulter, John Merle, 1851-1928; Chamberlain, Charles Joseph, b. 1863; Coulter, John Merle, 1851-1928. Morphology of spermatophytes. Part I. Gymnosperms. Chicago, University of Chicago Press
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