. An introduction to the structure and reproduction of plants. Plant anatomy; Plants. STRUCTURE AND DEVELOPMENT OF SPORANGIA 299 g-ranular thin-walled cells of the tapetum, which thus disorganises before the sporangium matures. Witli the ripening of the sorus the indusium dries and shrivels, exposing the sporangia, which likewise begin to lose moisture. As evaporation proceeds, the thin outer walls of the annulus. Fig. 166.—Nephrodium fiUx-mas. A, Mature spores, greatly magnified. B, A single sporangium, showing the annulus [an.) and stomium (s.). C, Early stages (I—IV) in the development of t
. An introduction to the structure and reproduction of plants. Plant anatomy; Plants. STRUCTURE AND DEVELOPMENT OF SPORANGIA 299 g-ranular thin-walled cells of the tapetum, which thus disorganises before the sporangium matures. Witli the ripening of the sorus the indusium dries and shrivels, exposing the sporangia, which likewise begin to lose moisture. As evaporation proceeds, the thin outer walls of the annulus. Fig. 166.—Nephrodium fiUx-mas. A, Mature spores, greatly magnified. B, A single sporangium, showing the annulus [an.) and stomium (s.). C, Early stages (I—IV) in the development of the sporangium (after Miillcr). D and E, Successively later stages. a., archesporium; ap., apical cell ; g., gland ; St., cells of stalk ; t., tapetum ; iv., wall. F, Germinating spore {sp.). p., beginning of prothallus ; r., rhizoid. commence to bulge inwards (cf. Figs. 165 and 166, B), owing to the gradual reduction in the volume of their sap. Thus an increasing tension is set up in the annulus,^ which e^•entually 1 It will be realised that the side-walls of the annulus are much less thickened than the horizontal walls, so that the contraction is entirely in the longitudinal 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 Fritsch, Felix Eugene, 1879-; Salisbury, E. J. (Edward James), Sir, b. 1886. London, G. Bell and sons ltd.
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectpl, booksubjectplants
