. Fossil plants : for students of botany and geology . Paleobotany. Fio. 241. A. Angiopteris evecta. (Cousiderablj' reduced.) B. Marattia fraxinea. Stipule. elliptical sori near the edge of the pinnules, consist of free sporangia (fig. 242, A—D) provided with a peculiar type of "annulus "2, in the form of a narrow band of thicker-walled cells, which extends as a broad strip on either side of the apex. An examination of sections through the sporangia of Angiopteris in different planes'' illustrates the difficulty of determining the precise nature of the annulus in a petrified spo
. Fossil plants : for students of botany and geology . Paleobotany. Fio. 241. A. Angiopteris evecta. (Cousiderablj' reduced.) B. Marattia fraxinea. Stipule. elliptical sori near the edge of the pinnules, consist of free sporangia (fig. 242, A—D) provided with a peculiar type of "annulus "2, in the form of a narrow band of thicker-walled cells, which extends as a broad strip on either side of the apex. An examination of sections through the sporangia of Angiopteris in different planes'' illustrates the difficulty of determining the precise nature of the annulus in a petrified sporangium which is seen only in one or two planes. Many of the sporangia from the English Coal-Measures, compared by authors with those of Leptosporangiate ferns, are in all probability referable to the Marattiaceous type. The vascular system* of the stem constitutes a highly complex dictyo- stelic or polycylic type which may consist of as many as nine concentric series of strands of xylem surrounded by phloem, with large sieve-tubes ^ Observed in plants in the Botanic Gardens of Brussels and Leipzig. 2 For an account of the spore-producing members of the Marattiaceae, see Bower (97). 3 Zeiller (90) p. 19. * Shove (00); Tansley (08).. 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 Seward, A. C. (Albert Charles), 1863-1941. Cambridge : University Press
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Keywords: ., bookcentury1800, bookdecade1890, bookpublishercambr, bookyear1898
