. The origin of a land flora, a theory based upon the facts of alternation. Plant morphology. MATONINEAE 569 The process thus described may then be repeated in that central strand : it becomes cylindrical, forming the second vascular ring, which is still connected at the nodes with the foliar system (Fig. 319 b), and a fresh central strand originates internally from it : this in its turn becomes cylindrical in the most advanced types, but still maintains its connection with the middle and outer rings in the neigh- bourhood of the nodes. The whole development is in fact an extreme type of the p
. The origin of a land flora, a theory based upon the facts of alternation. Plant morphology. MATONINEAE 569 The process thus described may then be repeated in that central strand : it becomes cylindrical, forming the second vascular ring, which is still connected at the nodes with the foliar system (Fig. 319 b), and a fresh central strand originates internally from it : this in its turn becomes cylindrical in the most advanced types, but still maintains its connection with the middle and outer rings in the neigh- bourhood of the nodes. The whole development is in fact an extreme type of the progression described by Gwynne-Vaughan in other solenostelic He showed how an internal vascular system may arise by progres- sive elaboration from a local thickening of the margin of the leaf gap of the original solenostele. In Matonia this development is the same, but it may be twice repeated. It is indicated by the palaeophy- tological evidence that while the Matonia-type is an ancient one it is not among the earliest. This accords with the soral and anatomical char- acters ; for the sorus, though of the Gleicheniaceous type, and still form- ing its sporangia simultaneously as in other Simplices, shows an advanced feature in the indusium, as also in the lateral dehiscence, and small spore-output. Anatomically the indi- cations are of the same nature : Matonia accords with G. pectinata in the solenostelic structure, but carries that line of elaboration much further. Finally, in the rhizomic habit and in the branching of the leaf there appears to be further similarity : there is indeed sufficient reason to regard the Matonineae as a family related to the Gleicheniaceae, but advanced in several respects beyond that type,, in directions which are represented more fully in other series of Fig. 319. At'ato.'Ua pectinata, drawings from wax models of the .stelar system. A =froni a young stem showing node. Z>' = from an older stem, showing node seen from behind. C=
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