An interesting example of a small shoot, the largest diameter of which is 2·8 cm., is shown in fig. 154, A: the section was cut a short distance above the bifurcation of the stele into two approximately equal branches. The outer part of the cortex consists of phelloderm, _pd_, with the usual rows of secretory tracts, and primary outer cortex _g_; the middle cortex is represented by patches of parenchyma with a few leaf-traces. To one of the steles, _s′_ (fig. 154, A), a crescent-shaped band of secondary xylem has been added; the other stele, _S_, possesses no fully developed secondary elements. Fig. 154, B and C, illustrates the anatomical features immediately external to the primary xylem of the smaller stele, _s_. The comparatively broad band of radially disposed parenchyma, _m_, is connected with the outermost elements of the xylem by a few rather dark and small crushed parenchymatous cells. The band _m_, which we may speak of as the meristematic zone, clearly consists of cells in a state of division; it is in this region that the secondary xylem is produced. Beyond the leaf-trace, (fig. 154, C, _lt_), occurs a portion of the secretory zone, some of the smaller cells of which show signs of disorganisation; but most of this tissue has been destroyed (fig. 154, B, _sc_). The outer edge of the secretory zone is shown in fig. 154, D abutting on the cells of the inner cortex, _c′_. The leaf-trace shown in the inner cortex in fig. 154, B illustrates the more oval or tangentially extended form of the xylem in this region, in contrast to the more circular outline which it exhibits on the inner side of the secretory zone. [Illustration: FIG. 155. _Lepidodendron vasculare_. Outer edge of secondary xylem: _m_, meristematic zone; _mr_, medullary ray. (Drawn from the section shown in fig. 168, A).]