. Fossil plants : for students of botany and geology . Paleobotany. 294 FILICALES [CH. Hymenophyllaceae. (Hymenophyllum, Trichovianes.) The sporangia, which are attached to a columnar receptacle or prolongation of a vein beyond the margin of the lamina, are characterised by an obliquely transverse annulus (fig. 224, C). A cup-like indusium surrounds the lower portion of the receptacle which is two-lipped in Trichomanes and entire in Hymeno- phyllum (fig. 270, C, D). These two filmy ferns have a wide distribution both in tropical and extra-tropical regions; they. Fio. 229. A. Thyrsopteris elega
. Fossil plants : for students of botany and geology . Paleobotany. 294 FILICALES [CH. Hymenophyllaceae. (Hymenophyllum, Trichovianes.) The sporangia, which are attached to a columnar receptacle or prolongation of a vein beyond the margin of the lamina, are characterised by an obliquely transverse annulus (fig. 224, C). A cup-like indusium surrounds the lower portion of the receptacle which is two-lipped in Trichomanes and entire in Hymeno- phyllum (fig. 270, C, D). These two filmy ferns have a wide distribution both in tropical and extra-tropical regions; they. Fio. 229. A. Thyrsopteris elegans. B. Cyathea spinulosa. C. Davallia concinna. D. coniifoUa. E. Alsophila excelsa. F, G. Dicksonia culcita. (A, after Diels and Kunze ; B, D, F, G, after Hooker ; E, after Bower.) are represented in the British Isles by Hymenophyllum tun- hridgense, H. Wilsoni, and Trichomanes radicans. Cyatheaceae. (Cyathea, Hemitelia, Alsophila, Dicksonia, Thyrsopteris.) The sporangia occur in indusiate or naked sori and have an obliquely vertical and incomplete annulus (fig. 229, E). In the great majority of cases the fronds are large and highly com-. 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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