. Morphology of gymnosperms. Gymnosperms; Plant morphology. CYCADALES 99 persist above the plate more or less, in one case for a distance of mm., above which a siphonostele is established. The develop- ment of the tetrarch root is delayed, its four protoxylem poles being inserted upon the cotyledbnary bundles, and the entire xylem system of the root being bordered periphe- rally by cambium. The single cotyle- don, which is often lobed at tip, is mul- ti fascicular, usually with alternating mucilage ducts, but all the vascular strands are derived from three bundles that connect with the vas
. Morphology of gymnosperms. Gymnosperms; Plant morphology. CYCADALES 99 persist above the plate more or less, in one case for a distance of mm., above which a siphonostele is established. The develop- ment of the tetrarch root is delayed, its four protoxylem poles being inserted upon the cotyledbnary bundles, and the entire xylem system of the root being bordered periphe- rally by cambium. The single cotyle- don, which is often lobed at tip, is mul- ti fascicular, usually with alternating mucilage ducts, but all the vascular strands are derived from three bundles that connect with the vascular plate (figs. 76, 77). These three strands are not of the same rank, and their relation to the vascular plate of the transition region should be under- stood. Two of the angles of this plate are directed toward the center of the two cotyledons (the usual abortion of one cotyledon in Ceratozamia does not affect this orientation), and therefore may be called cotyledonary; and the other two are in the plane between the two cotyledons, and there- fore may be called intercotyledonary. The median vascular strand that enters a cotyledon is connected directly with the adjacent cotyledonary angle or pole of the vascular plate, and therefore is a. Fig. 75.—Ceratozamia mexicana: transverse section of vascular plate of seedling, showing the protostelic con- dition; px, protoxylem; X225.—After Sister Helen Angela (59).. 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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