. Morphology of gymnosperms. Gymnosperms; Plant morphology. 104 MORPHOLOGY OF GYMNOSPERMS. Fig. 8o.—Dioon edule: semi-diagrammatic reconstruction of part of vascular system of em- bryo; cot, cotyledon; ib, tubular part of cotyle- dons; cs, cotyledonary strands; li-li, foliar strands of first leaf; li-li, foliar strands of second leaf; vp, vascular plate; o, protoxylem elements continuing downward into the hypo- cotyl.—After Thiessen (62). bial stage of the strand, and that its final course is laid down from the beginning. The seedlings of Zamia (Z. floridana and Z. integri- folia) have been st
. Morphology of gymnosperms. Gymnosperms; Plant morphology. 104 MORPHOLOGY OF GYMNOSPERMS. Fig. 8o.—Dioon edule: semi-diagrammatic reconstruction of part of vascular system of em- bryo; cot, cotyledon; ib, tubular part of cotyle- dons; cs, cotyledonary strands; li-li, foliar strands of first leaf; li-li, foliar strands of second leaf; vp, vascular plate; o, protoxylem elements continuing downward into the hypo- cotyl.—After Thiessen (62). bial stage of the strand, and that its final course is laid down from the beginning. The seedlings of Zamia (Z. floridana and Z. integri- folia) have been studied recently by Matte (68) and are found to confirm the results obtained from the preceding genera. The vascular plate of the cotyle- donary node is a protostele, and each cotyledon receives three vascular strands, as described for Ceratozamia. At the base of the cotyle- don the strands are mesarch or even concentric, but in the middle, region they be- come exarch and remain so to the tip, where transfusion tissue occurs and probably has replaced the centripetal xylem. The tap root is of the usual tetrarch type, be- coming reduced to triarch or even diarch toward the tip. The study of the seed- lings of Microcycas by Sister Helen Angela (65) con- firms the general situation described for Ceratozamia, Dioon, and Zamia, and shows some interesting variations. Microcycas is peculiar in the extensive. 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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