Abstract
Modern classifications of the ferns and lycosphens (fern-allies) group them into various Classes, all of which along with the Gymnospermae and Angiospermae are called the Tracheophyta (vascular plants), in allusion to the development of a vascular system, in distinction to the Bryophyta and other lower, non-vascular groups. There are four classes of Tracheophyta now recognized. The Psilopsida include Psilotum and Tmesipteris; the Lycopsida, Lycopodium, Selaginella, and Isoetes; the Sphenopsida, Equisetum; and the Pteropsida, the Filicineae (ferns), Gymnospermae, and Angiospermae. The first three, along with the Filicineae, were formerly grouped as Pteridophyta in older classifications. In earlier years the forms for names above the rank of genus were not definitely prescribed, and the same name was often used to represent an order, a family, or a tribe, without change in the termination.' The present International Code of Botanical Nomenclature (1952) specifies the terminations to be used: Divisions to end in
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