Observations on Petiolar Branching and Foliage of an American Botryopteris

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Abstract
A description of petiolar branching and of the frond-like nature of the ultimate segments of an American member of the genus Botryopteris is presented. Lateral traces arise from the petiolar or pinna traces by the separation of a portion of one of the lateral arms which in turn becomes trident. Lobed pinnules are borne on pinnae characterized by two longitudinally extending ridges on the adaxial surface. Since the method of petiolar branching of B. forensis as suggested by earlier writers is very probably in error, no significant anatomical distinction can be made among B. forensis, B. americana, and the specimens described in this paper. The presence of leaves on at least one member of the genus Botryopteris is a relatively advanced feature in contrast to the three-dimensional branching of the lower portions of the petiole. This condition can be derived from a telomic branching system and may be considered transitional between such a condition and an essentially two-dimensional fern frond.

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