sides of the larger tracheal strand, _cp_, separated, except at the base of the arch, by a small amount of conjunctive parenchyma from the centripetal xylem. The phloem is not preserved and is represented only by a few patches, _ph_, below the centrifugal tracheids. Dr Benson[566] in her account of this type of leaf gives additional details and compares the anatomical features with those in other species. The dual nature of the xylem like that characteristic of recent Cycads has usually been regarded as a definite feature of Cordaites leaves; Dr Stopes, on the other hand, interprets the narrower tracheids (occupying a position similar to those in fig. 465) in some sections of a leaf identified with _C. principalis_ from Grand’ Croix, as an inner sheath of transfusion elements (‘primitive transfusion tissue’) possibly derived from the centripetal xylem with which it is clearly connected at the sides precisely as in fig. 465; but in the Grand’ Croix leaf the phloem is enclosed within the sheath of narrower tracheids and not external to it as it is in the section shown in fig. 465 and in a section of _C. lingulatus_ figured by Dr Stopes. It is, however, difficult to recognise any fundamental difference between the ‘inner transfusion tissue’ and centripetal xylem. The cells of the outer sheath in Dr Stopes’s specimens of _C. principalis_ have bordered pits on their walls and this character is mentioned also by Renault in other specimens. [Illustration: Fig. 465. _Cordaites_ leaf (_Cordaites Felicis_ Bens.), probably borne on a _Mesoxylon_ stem. _cp_, centripetal xylem; _ph_, phloem; _px_, protoxylem. (Kidston Coll. No. 2194.)]