. Carnegie Institution of Washington publication. 20S THE MARATTIALliS rangiophore in all of the living Ophioglossaceae is adaxial, while in the Marattiaceae the synangia are abaxial, is a serious objection to such a hypothesis; and the most plausible explanation at present seems to be that of a progressive sterilization ot part of the sporophyll itself and the expansion ot the sterile tissue into the broad lamina of the leaf bearing the separated sporangia or synangia upon its lower surface. It must he admitted that the difference between the sporophylls of the existing Marattiaceae ami those
. Carnegie Institution of Washington publication. 20S THE MARATTIALliS rangiophore in all of the living Ophioglossaceae is adaxial, while in the Marattiaceae the synangia are abaxial, is a serious objection to such a hypothesis; and the most plausible explanation at present seems to be that of a progressive sterilization ot part of the sporophyll itself and the expansion ot the sterile tissue into the broad lamina of the leaf bearing the separated sporangia or synangia upon its lower surface. It must he admitted that the difference between the sporophylls of the existing Marattiaceae ami those of the Ophioglossaceae is very great, and the leaves of the former, superficially at least, are much more like those of the leptosporangiate ferns; but the sporangia themselves are very similar in then development to those of the 0 *&~. A. Lower surface of a sporophyll of Kaulfussia, showing circular synangia. X i .5. B. Median section of a synangium. â '-â C, I). Cross-sections of a synangium* C. Near top, showing openings of loctili. D. Near middle. X12. Ophioglossaceae, and offer no obstacle to the assumption of a fairly close relationship between the Ophioglossaceae and the Marattiaceae, which is indicated by the history of the development of the gametophyte, and the vegetative organs and tissues of the sporophyte. Perhaps the most marked difference between the tissues of the Marat- tiaceae and the Ophioglossaceae is the prevalence of the mucilage ducts in the tissues of Marattiaceae, but these arise rather late in the history of the sporophyte, and it is. 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 Carnegie Institution of Washington. Washington, Carnegie Institution of Washington
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