. The origin of a land flora, a theory based upon the facts of alternation. Plant morphology. GLEICHENIACEAE 561 be the final decision on this point, it is clear that sori of the same type as those of Gleichenia existed at the Carboniferous period, and that in size and form the constituent sporangia were like those seen in the living species. Anatomy. There is greater uniformity of anatomical structure in the Gleicheniaceae than in the Schizaeaceae; but still there are marked differences within the family which have a probable phyletic bearing when placed in relation. Fig. 313. A = diagram of
. The origin of a land flora, a theory based upon the facts of alternation. Plant morphology. GLEICHENIACEAE 561 be the final decision on this point, it is clear that sori of the same type as those of Gleichenia existed at the Carboniferous period, and that in size and form the constituent sporangia were like those seen in the living species. Anatomy. There is greater uniformity of anatomical structure in the Gleicheniaceae than in the Schizaeaceae; but still there are marked differences within the family which have a probable phyletic bearing when placed in relation. Fig. 313. A = diagram of the tissues of the rhizome of Gleichenia Jiabellata. X8, i?=section of the stele (somewhat diagrammatic) of C. jiectiiuita. X 26. C=part of the stele of G. dichotoma. â X 350. (All after Boodle, from Campbell's Mosses and Ferns.') to other In the majority of species the rhizome shows in the internodes a centrally placed, solid stele (protostele), consisting of a central mass of xylem composed of tracheides and parenchyma, and surrounded by a continuous ring of phloem, pericycle, and endodermis (Fig. 313 a). There is thus a general resemblance to the structure of the rhizome of Lygodium; but a point of difference is that whereas in Lygodium there is no typical protoxylem, in Gleichenia the protoxylem is represented by several distinct groups of spiral elements, which are mesarch. The tracheides of the xylem are arranged in chains and groups separated by parenchyma: in fact the structure as seen in G. flabellaia is strikingly like that of Lygodium, except in the matter of the protoxylem. In several aThe data here embodied are chiefly derived from Poirault, Ann. Sci. Nat. Bot., 7 SiSrie, T. xviii., p. 170, etc., and from Boodle, Ann. of Bot., vol. xv., p. 703. 2 N. 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
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