Filicinae

Abstract

In the basic work of modern taxonomy, the Species Plantarum 1753 of Linnæus, the Pteridophyta formed the first order, Filices, of the 24th class Cryptogamia. Linnæus described 12 genera of ferns with 192 species besides 4 genera of “fern-allies” (Equisetum, Mar-silia, Pilularia, Isoetes), while Lycopodium was placed in the second order: Musci. Linnæus based his genera exclusively upon the characters of the sori (superficial or marginal, round, linear or confluent, etc.) thus using the same characters of genera which almost all pteridologists regarded as the most important ones for a century and a half. The sporangia and spores were the only organs of reproduction known for a century and were believed to play the same rôle as the flowers of the Phanerogams and their characters were naturally considered as being of principal taxonomic value. During the latter half of the 18th century several botanists (e.g. Adanson and J. E. Smith) found that the sori of some ferns were covered with a protecting membrane, the indusium, which was absent in others, and this difference, not used by Linnæus, was found important enough, not only to split up the Linnæan genera but also to arrange all genera in two series, Indusiatae and Exindusiatae, which treatment was followed by almost all the pteridologists of the 19th century.