Summary.1The tissues of the fossil fernAnkyropteris corrugatashow well‐marked reactions to wounding.2In the root these, which consist of irregularly disposed wedges of meristematic tissue, are confined to the cortical parenchyma and may extend for some distance beyond the actual wound area.3In the stem the wounds generally take the form of irregular cortical fissures. These are bordered on either side by a strip of meristem four to eight cells in depth.4Anomalous secondary xylem which occurs in a stem in the neighbourhood of a bifurcation is also considered to be due probably to traumatic stimulus.5In the petiole the wound reaction varies.6Where the wound is superficial a pad of healing meristem is developed from the cortical cells. The parenchymatous cells are most active, but the sclerenchymatous cells may also undergo division. Exceptionally the superficial cells may be modified in a similar way to those of the normal epidermis, thus providing an example of “restitution.”7Other wounds, termed “crush” wounds, are characterised by irregular cortical fissures. These become bordered or surrounded by a strip of meristematic cambiform cells.8Where the wounds are deep‐seated the vascular tissues may be involved in the reaction.9The reaction in such cases takes the form of the development of secondary tracheids, usually short and of small calibre, which vary in position with that of the wound.10There is some evidence that the phloem or phloem‐parenchyma may also become meristematic under the