. Fossil plants : for students of botany and geology . Paleobotany. IVJ CONDITIONS OF PRESERVATION. 91 seeds were deposited in the sandy sediment. Delicate leaf structures with sporangia still intact, point to quietly flowing water and a transport of no great distance. Occasionally the. Fig. 19. Piece of Coal-Measures Sandstone with oasts of Trigonocarpon seeds, from Peel Quarry near Wigan. From a specimen in the Manchester Museum, Owens College. ^ nat. size. large number of delicate and light plant fragments, associated it may be with insect wings, may favour the idea of a wind storm which sw
. Fossil plants : for students of botany and geology . Paleobotany. IVJ CONDITIONS OF PRESERVATION. 91 seeds were deposited in the sandy sediment. Delicate leaf structures with sporangia still intact, point to quietly flowing water and a transport of no great distance. Occasionally the. Fig. 19. Piece of Coal-Measures Sandstone with oasts of Trigonocarpon seeds, from Peel Quarry near Wigan. From a specimen in the Manchester Museum, Owens College. ^ nat. size. large number of delicate and light plant fragments, associated it may be with insect wings, may favour the idea of a wind storm which swept along the lighter pieces from a forest-clad slope and deposited them in the water of a lake. In some Tertiary plant-beds the manner of occurrence of leaves and flowers is such as to suggest a seasonal alternation, and the different layers of plant debris may be correlated with definite seasons of growth^. The predominance of certain classes of plants in a particular bed may be due to purely mechanical causes and to differential sorting by water, or it may be that the district traversed by the stream which carried down the fragments was occupied almost exclusively by one set of plants. The trees from higher ground may be deposited in a different part of a river's course to those growing in the plains or lowland marshes. It is obviously impossible to lay down any definite rules as to the reading of plant records, as aids to the elucidation of past physical and botanical conditions. Each case must be separately considered, and the various probabilities taken into account, judging by reference to the analogy of present day conditions. Various attempts, more or less successful, have been made 1 Heer (55).. 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 : U
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Keywords: ., bookcentury1800, bookdecade1890, bookpublishercambr, bookyear1898
