In experiments to determine the flotation characteristics of fresh horsetails (Equisetum arvense) as an aid for interpreting fossil giant horsetails (Calamites), 63 percent of 140 Equisetum arvense floated vertically or stood erect on the tank bottom before complete saturation. Use of fresh- or saltwater gave no appreciable differences. Duration of vertical stance ranged from a few hours to several days, depending on factors of length and freshness. These results suggest that upright fossilized Calamites stems may not be in situ, especially if they are single stems unattached to basal rhizomes and if paleo-ecological and sedimentary evidence also suggests transport.

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