The annexed figure, [Lign. 37], represents the transverse section of a small Stigmaria, with the axis displaced from its natural situation; this circumstance, as well as the corresponding external groove, has arisen from compression, by which the tough cylinder has been forced from its original position in the middle of the soft cellular tissue, to one side.
Lign. 37. Transverse Section of Stigmaria ficoides; nat.
(M. Adolphe Brongniart.)
This specimen shows that the cylinder (a in [Lign. 36]) is formed of bundles of vascular tissue, disposed in rays.
The central axis is thus shown to be a cylinder composed of bundles of vessels, disposed in a radiating manner, and separated from each other by medullary rays; the whole constituting a ligneous zone resembling that of Sigillaria (see [Lign. 35]); but the inner circle of medullary tissue seen in the latter is altogether wanting. This difference is similar to that observable in the stems or branches of a dicotyledonous tree, in which the woody cylinder is associated internally with bundles of medullary tissue, and the roots of the same tree that are destitute of them. Part of a vascular bundle from the woody tissue of a Stigmaria, seen by a high power and transmitted light, is figured [Pl. V. fig. 6]; the smooth interspaces are composed of cellular tissue.
Lign. 38. Erect Stem of a Sigillaria, with roots.
Coal Mine, near Liverpool.
| a. | The trunk of the tree, traversing a bed of Coal. |
| b. | The roots (Stigmariæ) spreading out in the Under-clay. |
ERECT SIGILLARLA WITH ROOTS.