Acrogens

Acrogens (Gr., 'summit-growers'), a term applied to the higher cryptogamic plants in which root, stem, and leaf are usually distinctly developed—e.g. ferns, club-mosses, horsetails, &c. The name refers to the structure and growth of the stem in which the vascular bundles when present are 'simultaneous' (see STEM) in development, and growth occurs only at the apex, while increase in thickness is effected by the coherence of leaf-bases or the formation of roots. Of this 'acrogenous' growth, tree-ferns are the best examples. The term has, however, fallen into disuse, along with the terms Exogen and Endogen (q.v.), on account of the erroneous views of dicotyledonous and monocotyledonous stem-growth which these latter respectively imply.