A much older section is shown in part in fig. 210, E. The secondary xylem cylinder, _St_, is shown in the lower part of the section; beyond this is a band of secondary tissue which reaches in some places a breadth of 6 cm. The greater part of this tissue consists of phelloderm of very uniform structure made up of radial series of cells: this is interrupted in most parts of the section by a gap crowded with intruded rootlets (a portion of this is enlarged in fig. 210, D). Beyond this gap the secondary tissue consists of radial series of cells characterised by the considerable tangential elongation of many of the elements, precisely like the tissue figured by Williamson. In all probability the gap represents a line of weakness due to the phellogen, and if this is the case it is clear that in an old _Stigmaria_ the phelloderm exceeded in amount the tissue formed external to the phellogen. The secondary tissue on the inner side of the phellogen is characterised by numerous irregular concentric lines superficially resembling rings of growth in the wood of a Conifer: these are, however, not the result of any periodic change in external conditions, but are apparently due to crushing of the tissue and are possibly, to some extent, the result of the presence of secretory strands like those in the phelloderm of _Lepidodendron_. The surface of this older rhizome retains patches of primary tissue, and an occasional rootlet, as at _r_, fig. 210, E, is seen in connexion with the cortex; the cortex has been vertically fissured as the result of secondary growth and presents an appearance like that shown in _Lepidodendron Wünschianum_ and _L. Veltheimianum_ (figs. 181, A, and 186, A).