Pseudocotyledoneae, Agardh; Heteronemeae, Fries; Acrobrya, Mohl, Endlicher.
Characters.—Substance of the plant composed of cellular tissue chiefly, and, in the higher forms, of vessels. Cuticle bearing stomata or breathing pores. Stem and leaves distinguishable. Opposition of stem and root. Stem growing at the point only.
This class includes a number of Orders, of which two only (viz. Lycopodiaceae and Filices) need be here noticed as yielding anything useful in medicine.