Vestured Pits in Wood of Onagraceae: Correlations with Ecology, Habit, and Phylogeny
All Onagraceae for which data are available have vestured pits on vessel-to-vessel pit pairs. Vestures may also be present in some species on the vessel side of vessel-to-ray pit pairs. Herbaceous Onagraceae do not have fewer vestures, although woods with lower density (Circaea L. and Oenothera L.) have fewer vestures. Some Onagraceae from drier areas tend to have smaller vessel pits, and on that account may have fewer vestures (Epilobium L. and Megacorax S. González & W. L. Wagner). Pit apertures as seen on the lumen side of vessel walls are elliptical, occasionally oval, throughout the family. Vestures are predominantly attached to pit aperture margins. As seen from the outer surfaces of vessels, vestures may extend across the pit cavities. Vestures are usually absent or smaller on the distal portions of pit borders (except for Ludwigia L., which grows consistently in wet areas). Distinctive vesture patterns were observed in the several species of Lopezia Cav. and in Xylonagra Donn. Sm. & Rose. Vestures spread onto the lumen-facing vessel walls of Ludwigia octovalvis (Jacq.) P. H. Raven. Although the genera are presented here in the sequence of a recent molecular phylogeny of Onagraceae, ecology and growth forms are more important than evolutionary relationships with respect to abundance, degree of grouping, and morphology of vestured pits. Designation of vesture types is not warranted based on the distribution of named types in Onagraceae and descriptive adjectives seem more useful, although more data on vesturing in the family are needed before patterns of diversity and their extent can be fully ascertained. Vestures are less common and may have a more complicated genetic basis than helical thickenings in vessels, but may be a more effective form of water column maintenance.