Wood anatomy of the tribe Millettieae with comments on related papilionoid Leguminosae

Abstract

The tribe Millettieae has traditionally included some 43 to 47 genera although more recent phylogenetic evidence has shown that a smaller core-Millettieae group of c. 23 genera may form part of a recircumscribed Millettieae sensu stricto. We have examined the wood of 27 genera, 16 of which are in the core-Millettieae and the remaining 11 belong in 4 groups, mostly with closer affinities outside Millettieae s.str. The wood anatomy of the various genera is nevertheless very uniform. Most genera are diffuse porous with no predominant vessel pattern. They have paratracheal parenchyma ranging from scanty through vasicentric, aliform and confluent, and often banded. Rays are mainly up to 5 cells wide. Axial parenchyma and rays are nearly always storied. The lianas Paraderris elliptica, Derris uliginosa, Ostryocarpus cf. riparius and Wisteria spp. have alternating bands of xylem and phloem, which are also found in some Dalbergieae. Even in the genera without such anomalous secondary growth there are many similarities between the wood of Millettieae and Dalbergieae. The wood of some genera in Sophoreae and Swartzieae is also compared. Our observations will be put in the context of recent cladistic analyses on both morphological and molecular data by other authors.