Report of the Committee on Paleoecology, 1935-1936: Presented at the Annual Meeting of the Division of Geology and Geography, National Research Council, May 2, 1936 (1936) / Chapter Skim
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Paleozoic Plants and their Environmental Relations - Chester A. Arnold
Paleozoic Plants and their Environmental Relations - Chester A. Arnold
Pages 55-65
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From page 55... ...
The problan of environmental adaptations of Paleozoic plants differs materially from that of Mesozoic end Tertiary plants in that all Paleozoic types are extinct and their nearest living relatives are so remote that ecological comparisons are difficult to make. Predominant among the Paleozoic plant types were.
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From page 56... ...
The difficulty, however, in applying the same inferences to Paleozoic plants is that very pronounced structural adaptations are not common anong plants growing under normal surroundings. It is only when plants are subject to extreme conditions, as aridity, salinity, etc., that they develop specialized structures which are conspicuous enough to be recognized in Paleozoic plants and a similar environment postulated for than.
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From page 57... ...
During the process of transportation'of plant remains from the place where they grew to the place of final deposition a kind of "sorting out" process may occur, and not all of the components of the flora of a given locality will always remain in recognizable form in the ultimate deposit. Such factors as distance from shore, direction of currents, presence of petrifying minerals, rate of deposition of sediments, and a-number of other things usually exert a selective influence by setting up an environment of deposition suitable for the preservation of some plants but not for others of the seme plant association.
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From page 58... ...
These had been variously identified as Calamites, Pseudobornia and Callixylon, but a careful examination showed them to be indistinguishable from water soaked woody plant debris which had become cross-cracked as a result of frequent wetting and drying (5)
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From page 59... ...
'AS with certain living species, of which the bracken fern is a stock example, it is quite possible that certain Paleozoic species were able to tolerate a considerable range of temperature, although specific examples cannot be cited. The presence or absence of growth rings- or "annual rings" in Paleozoic ' stems is often employed as evidence concerning climate.
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From page 60... ...
Seasonal fluctuations of either moisture or temperature have little effect on the development of the rings although indistinct rings seem to form in these trees under most any natural outdoor •onditions. On the other hand, the common persimmon, Diospyros virginiana, has been observed to develop absolutely uniform wood in an unchanging climate, but when the same species is subjected to seasonal fluctuations well marked rings will form (1)
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From page 61... ...
Although growth rings in Paleozoic woods cannot be interpreted as constituting evidence of marked seasonal fluctuations within that era, it is impossible to explain them on other grounds than that they reflect seasonal changes of some sort. Without seasonal variations of some kind it is impossible to account for the origin of regular growth rings in the first place.
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From page 62... ...
Unless' there was an inadequately developed root system it is difficult to understand the utility value of such structures except for plants subject to extreme aridity. However, if the plants grew in situations where there was a marked seasonal lowering of the water level the accompanying dryness might account for the presence of such cavities.
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From page 63... ...
Sufficiently pronounced structural features in Paleozoic plants may indicate adaptations of a certain kind if comparable adaptations can be recognized in living forms. Environmental conditions varied in .time and place during the Paleozoic, and sweeping conclusions regarding temperature, seasonal fluctuations and humidity should not be drawn from plants within a limited area or restricted horizon.
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From page 64... ...
The Upper Devonian forest of seed ferns in eastern New York. New York State Mus.
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