Hueber, Francis M., and James D. Grierson. (Cornell U., Ithaca, New York.) On the occurrence of Psilophyton princeps in the early Upper Devonian of New York. Amer. Jour. Bot. 48(6): 473–479. Illus. 1961.—Although several critical studies of Psilophyton princeps have limited its range to Lower and Middle Devonian, the writers have been able to identify plant remains from the Upper Devonian as P. princeps. Specimens prepared by maceration and transfer techniques demonstrate positive agreement of characteristics of the spines, cuticle and vasculature with P. princeps from Canada and Scotland.
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Hueber et al. (1961) studied this question.
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