. The origin of a land flora, a theory based upon the facts of alternation. Plant morphology. MATONIA-DIPTERIS SERIES 62 1 show no regularity of position or of orientation, such as is seen in Matonia: there is also an absence of any projecting receptacle. The sporangia of the same sorus have been found to arise simultaneously in D. Lobbiana, which may in this respect compare with Matonia. But in D. conjugata they are formed successively, while those which appear later are distributed without order amongst those first formed. The sorus, in this respect, compares with that of the Mixtae, but the
. The origin of a land flora, a theory based upon the facts of alternation. Plant morphology. MATONIA-DIPTERIS SERIES 62 1 show no regularity of position or of orientation, such as is seen in Matonia: there is also an absence of any projecting receptacle. The sporangia of the same sorus have been found to arise simultaneously in D. Lobbiana, which may in this respect compare with Matonia. But in D. conjugata they are formed successively, while those which appear later are distributed without order amongst those first formed. The sorus, in this respect, compares with that of the Mixtae, but the succession is not long main- tained. When the individual sporangia are examined an essential difference is found from the Polypodiaceous sporangium, with its vertical ring; for here the annulus is not only oblique, but also twisted : the series of cells of the annulus can be traced laterally past the insertion of the stalk, but the induration of their walls is interrupted at that point: the. Fig. 346. Dipteris conjugata, Rein. Portion of leaf, showing the extended surface, the webbing between the pinnae, the venation, and the numerous sori spread over the surface. Natural size. Figs. 344-346, after drawings by Mr. A. K. Maxwell. dehiscence is lateral, but there is no clearly denned stomium. The sporangium itself is small, and the spore-output has been found both in D. Lobbiana and in D. conjugata to approach the typical number of 64. Comparing this sporangial structure with that of other Ferns, it is actually most like that of the Cyatheae, though the interrupted induration of the annulus points a further departure from the primitive type, such as may with reasonable probability be found in the sporangia of Matonia, and ultimately of Turning to the anatomical characters, they bear out the above com- parison ; for the rhizome contains a simple solenostele, while the leaf-trace comes off a single ribbon-like strand, opening a leaf-gap which soon closes again. Th
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