. The origin of a land flora, a theory based upon the facts of alternation. Plant morphology. Fig. 58. Tmesipteris Tannensis, Bernh. A, median section through synangium, showing the tissue where the septum normally is developing a*, sporogenous cells (s). ^ = tapetum. B, part of the contents of a similar synangium, rather older, xx shows the line where the septum should normally be, while a chain of fertile cells stretches continuously across it. x 100. The conversion of potentially fertile cells into vegetative cells was recognised by Naegeli, and embodied by him in his fundamental law of org
. The origin of a land flora, a theory based upon the facts of alternation. Plant morphology. Fig. 58. Tmesipteris Tannensis, Bernh. A, median section through synangium, showing the tissue where the septum normally is developing a*, sporogenous cells (s). ^ = tapetum. B, part of the contents of a similar synangium, rather older, xx shows the line where the septum should normally be, while a chain of fertile cells stretches continuously across it. x 100. The conversion of potentially fertile cells into vegetative cells was recognised by Naegeli, and embodied by him in his fundamental law of organic development, as follows: " The phenomenon of reproduction of one stage becomes at a higher stage that of vegetation. The cells which in the simpler plant are set free as germs, and constitute the initials of new individuals, become in the next higher plant part of the individual organism, and lengthen the ontogeny to a corresponding ;2 The sterilisation seen in the sporophyte of the Archegoniatae and Seed-Plants is only one special case of that included under Naegeli's general law. He points out that the law is realised in three different ways, and the case for the sporophyte generation, with which alone we are at present concerned, falls under the first head, expressed by him as follows: " The propagative cells which arise by division are converted into tissue ; 1 Organbildung, p. 241. 2 Abstammungslehre, p. 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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