. The origin of a land flora, a theory based upon the facts of alternation. Plant morphology. 2 12 SYMMETRY OF THE SPOROPHYTE. Flu. 107. Diagrammatic representation of the end of a rhizome of Kaulfussia. w — wings of stipule; com = transverse commissure. (After Gwynne- Vaughan.) .o> in all the genera of Marattiaceae investigated hitherto is upright, bursting through the prothallus, not recumbent as in other Ferns (Fig. 105). In Angiopteris and Marattia this con- dition is maintained throughout life, and there is no reason to think other- wise than that these plants retain their primitive po
. The origin of a land flora, a theory based upon the facts of alternation. Plant morphology. 2 12 SYMMETRY OF THE SPOROPHYTE. Flu. 107. Diagrammatic representation of the end of a rhizome of Kaulfussia. w — wings of stipule; com = transverse commissure. (After Gwynne- Vaughan.) .o> in all the genera of Marattiaceae investigated hitherto is upright, bursting through the prothallus, not recumbent as in other Ferns (Fig. 105). In Angiopteris and Marattia this con- dition is maintained throughout life, and there is no reason to think other- wise than that these plants retain their primitive position. It is probably shared also by Archangiopteris;1 at all events there was no dorsiventrality in the only specimen with an axis hitherto examined. In the genus Danaea the same holds for D. simplicifolia; but certain other species of Danaea have an oblique rhizome, for instance, Danaea alata (Fig. 106). Comparison of a number of stocks of this Fern shows various degrees of inclination and curvature of the axis. It is upright at first, and produces leaves and roots uniformly on both sides of the axis; but later the axis arches over to one side, and a distichous arrangement of the leaves is approached, while the roots originate chiefly from the side directed downwards. In Kaulfussia these characters are more pronounced; for there the mature rhizome is horizontal, with marked dorsi- ventrality, and with internodes of appreciable length (Fig. 107). Unfortunately the early development of the sporophyte of Kaulfussia is still unknown. It seems a, reasonable interpre- tation of the facts that the upright position, with radial symmetry, as seen in Angiopteris and Marattia, was the primitive condition here as in other Vascular Plants: and that the oblique position, already seen in certain Danaeas, became more accentuated in the horizontal rhizome of Kaulfussia, with its marked dorsiventrality. The analogy with what is seen in the Ophio- glossaceae greatly strengthens this conclusi
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