Glossary of "Cladistics (2nd ed.)" by Kitching et al. (1998)
- A character in which the transformations in one direction cost a different number of steps from the transformations in the opposite direction. For example, in the directed character, 0 <-> 1, the transformation 0 -> 1 may cost one step but the reverse transformation, 1 -> 0 may cost two steps. Camin-Sokal and Dollo optimizations both use directed characters. Cf. undirected.
- Kitching, I. J., Forey, P. L. Humphries, C. J. & Williams, D. M. 1998. Cladistics, 2nd ed.: the Theory and Practice of Parsimony Analysis. -xii + 228 pp. Oxford University Press, New York.