Abstract
Ferns comprise both extant and fossil taxa displaying a broad morphological and anatomical disparity. In order to compare their features, we propose a knowledge base of 46 genera, 101 characters and 273 character states with illustrations, bibliographical references and annotations with terms from the Plant Ontology Consortium (amongst others). The knowledge base is designed with the Xper² program. Descriptions are exhaustive (i.e., all the taxa have been given values for every character) thanks to the management of inapplicable and missing data. The Xper² format is compatible with the standard interchange format Structured Descriptive Data (SDD). The user-friendly and intuitive environment provided by Xper2 should help users to take ownership of our conceptualization.