. The Annals and magazine of natural history; zoology, botany, and geology. Natural history; Zoology; Botany; Geology. 140 On Equisetum in the Yorkshire Coal-measures. the fossil, also enlarged, whose similar characters are observ- able. To return to fig. d, the central tubercle indicates the point at which the peltate-shield is attached to its stalk ; hence there is a greater thickness of tissue at this part, and in drying the peripheral portions of the shield shrink more, and, being unsupported underneath, fall below the level of the centre, and thus the central tubercle is formed. One of th
. The Annals and magazine of natural history; zoology, botany, and geology. Natural history; Zoology; Botany; Geology. 140 On Equisetum in the Yorkshire Coal-measures. the fossil, also enlarged, whose similar characters are observ- able. To return to fig. d, the central tubercle indicates the point at which the peltate-shield is attached to its stalk ; hence there is a greater thickness of tissue at this part, and in drying the peripheral portions of the shield shrink more, and, being unsupported underneath, fall below the level of the centre, and thus the central tubercle is formed. One of the peltate-shields is shown in profile at fig. e*, which illustrates more fully their a. Equisetum Hemingwayi, Kidston. Nat. size. b. Outer surface of one of the sporangiferous shields of Equisetum Hem- ingwayi. Enlarged. c. Cone of Equisetum limosum, Sm. X ±h ; from a photomicrograph. d. Outer surface of a sporangiferous shield of Equisetum limosum. En- larged. e. Sporangiferous shield of existing Equisetum seen in profile, to show central column and sporangia. Enlarged. Now though the internal structure of the fossil cones is unknown, I think we are quite warranted in supposing that the central tubercle and slightly elevated margins of the plates * From Maout and Decaisne, ' General System of Botany,' English ed. p. 904 (1873).. 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 London, Taylor and Francis, Ltd
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Keywords: ., bookce, booksubjectbotany, booksubjectgeology, booksubjectzoology
