. Devonian floras; a study of the origin of Cormophyta. Paleobotany -- Devonian. 38 THE PSILOPHYTON FLORA [CH. Distribution. Upper Devonian of Belgium, United States, Canada and Australia. This fertile shoot is at present wholly obscure, but it is very un- like any other organ known from more recent rocks. It is widely distributed in Devonian rocks. Parka. (Fig. 20.) Parka, Flemingi, 1831. Body small, of variable size, rarely ex- ceeding one or two inches across, more or less circular, lenticular, of very small thickness, containing many disc-like oval or circular masses, which in their turn c
. Devonian floras; a study of the origin of Cormophyta. Paleobotany -- Devonian. 38 THE PSILOPHYTON FLORA [CH. Distribution. Upper Devonian of Belgium, United States, Canada and Australia. This fertile shoot is at present wholly obscure, but it is very un- like any other organ known from more recent rocks. It is widely distributed in Devonian rocks. Parka. (Fig. 20.) Parka, Flemingi, 1831. Body small, of variable size, rarely ex- ceeding one or two inches across, more or less circular, lenticular, of very small thickness, containing many disc-like oval or circular masses, which in their turn contain spores. Distribution. Silurian and Lower Old Red, Scotland and England. Not known outside Britain. Don and Hickling^, in an im- portant and quite recent paper on this mysterious fossil, have shown conclusively that the disc-like masses of Parka undoubtedly contain spores and that the fossil is thus clearly of vegetable origin. In this matter they confirm the conclusions of Dawson and of Penhallow^ and more recently of Reid, Graham and Macnair^. Don and Hickling show that Parka consists of a flat, dorsiventral, multi-cellular and multi-layered thallus, develop- ing by marginal growth (Fig. 20, 1). The shape is roughly circular or oval; but lobate, reniform and even irregular forms occur. In size the thalli measure 5 mm. to 7 cm. across. The margin, Avhich is distinctly frilled, is usually less than 1 mm. broad. The rest of the thallus is composed of small oval 1 Fleming (1831). " Don and Hickling (1917). 3 Dawson and Penhallow (1891); Penliallow (1892). * Reid, etc. (1897) and (1899).. Fig. 19. Bdriiiojiii/jton Bichard- soni, (Daws.), from the Upper Devonian of the United States. After White (1905).. 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 Arber, E. A. Newell (Edward Alexander Newell), 187
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Keywords: ., bookcentury1900, bookdecade1920, bookpublishercambr, bookyear1921
