. The origin of a land flora, a theory based upon the facts of alternation. Plant morphology. 5i8 FILIC ALES marked a feature in Ferns at large that these irregularities command the greater attention. Fig. 286 a represents a tangential section traversing three sori in Danaea elliptica, of an age prior to the tetrad-division : the varying size of the sporangia is striking, as also their frequent grouping in pairs, separated by a thin, or even by a partial septum. Some of A B. Fig 286. Danaea elliptica, Smith. Drawings illustrating partial septations of the sporangium. A, tangential section thro
. The origin of a land flora, a theory based upon the facts of alternation. Plant morphology. 5i8 FILIC ALES marked a feature in Ferns at large that these irregularities command the greater attention. Fig. 286 a represents a tangential section traversing three sori in Danaea elliptica, of an age prior to the tetrad-division : the varying size of the sporangia is striking, as also their frequent grouping in pairs, separated by a thin, or even by a partial septum. Some of A B. Fig 286. Danaea elliptica, Smith. Drawings illustrating partial septations of the sporangium. A, tangential section through three sori, showing the loculi in ground plan : the septa are often thin, so that pairs of loculi are in close juxtaposition ; the loculi marked (jr) are large, and show one or more partial septa. X 20. B, C, D, E, show such loculi with partial septa in greater detail : in /' and E it is difficult to decide whether the cells marked (?) will develop as tapetum or as spore-mother-cells. X 150. these partially septate sporangia are represented more in detail in Figs. 286 b-e, From these drawings it is clear that the identity of the sporangium is not maintained: that where the initial sporogenous group is large, some of its cells may develop as transitory tapetum, or even as permanent cells of septal tissue : and thus various intermediate steps of completion of a septum may be observed. Somewhat similar conditions. 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 Bower, F. O. (Frederick Orpen), 1855-1948. London, Macmillan and Co. , Ltd.
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