Research Training Program Smithsonian Institution National Museum of Natural History PROJECT SUMMARY 1995
Christopher R. Hardy University of Maryland at College Park College Park, Maryland
Robert Faden, Ph.D. Project Advisor Department of Systematic Biology, Botany
Comparative leaf anatomy of Pollia and Commelina (Commelinaceae)
ABSTRACT

The anatomy of five species of Pollia and seventeen species of Commelina (Commelinaceae) is detailed here in a preliminary effort towards resolving the subtribal taxonomy within the tribe Commelineae. Past macromorphological and cytological investigations among the thirteen genera in the Commelineae have failed to resolve sufficient subtribal relationships, yet anatomy, among other characters, has proven valuable in resolving higher level relationships within the Commelinaceae and in delimiting eight subtribes in its sister tribe Tradescantieae (Faden & Hunt 1991). Providing a sound base for further anatomical investigations necessary in the Commelineae, this study has served to evaluate foliar anatomy for its diagnostic value and taxonomic utility, in addition to discovering 4-celled glandular microhairs (P. mannii) and 3-celled hook hairs (Commelina spp.) never before recorded for the Commelinaceae. Characters of potentially diagnostic value included those of diameter and shape of the middle cell of the glandular microhair, which is demonstrated here to be significantly larger in diameter and distinct in shape in Commelina than from those observed in Pollia. Several characters have also been shown to be of little taxonomic utility, yet with the suspicion that they may provide insight into structure-function relationships of leaf anatomy with the plants' ecology, habitat preference, and/or habit, and some (those of C. replans and C. purpurea) are purported to provide possible examples of anatomical convergence with species of Murdannnia (tribe Commelineae), which exhibit similar habit preferences.