Wood Anatomy of Primitive Angiosperms: New Perspectives and Syntheses

Abstract

The concepts of I. W. Bailey and his students Frost 1930a, Frost 1930b, Frost 1931 and Kribs 1935, Kribs 1937 concerning wood anatomy of dicotyledons as well as the work of Cheadle (1943) on xylem of monocotyledons were developed independently of evolutionary concepts in other fields such as embryology. Bailey was not unaware of developments in other fields, but he and the Harvard xylem students did not incorporate those developments in their work. There were advantages as well as disadvantages in the development of xylem data independently of work in other fields. In fact, if xylem evolution is influenced by long-term and short-term strategies for optimizing the water economy of a plant, xylem patterns ought to evolve entirely independently of patterns in, for example, pollination biology or defenses against herbivores. Ultimately, however, syntheses between xylem-evolution patterns and patterns from other fields are desirable. In particular, cladistic analyses based on a large number of morphological characters and cladistic analyses of DNA data invite comparison. There are some apparent conflicts between the traditional data on wood evolution and the newer cladistic results, and the purpose of this chapter is to examine what these apparent conflicts are and to point out possible methods of resolution for them. All of the discrepancies cannot be resolved, but there may be some value in highlighting what the discrepancies are, the concepts that may permit resolution, and the kinds of data that are needed.