The true external surface of the cortical investment is marked with longitudinal striæ, without any indications of joints or constrictions; but the position of the original articulations is indicated in some specimens by the presence of small verticillate scars, to which leaves were appended[78] as in the example figured by M. Brongniart, of which [Lign. 14, fig. 1], is a reduced figure.
[78] See Mr. Dawes, "On the Structure of Calamites," Proc. Geol. Soc, 1851, vol. vii. p. 197.
Lign. 15. Calamites, in Coal Shale.
| Fig. | 1.— | Calamites radiatus, with the remains of one of the sheaths.—1/2 nat. |
| 2.— | Stem, with remains of roots.—1/2 nat. | |
| 3.— | Calamites approximatus, showing the curved lower end of the plant.[79]—1/5 nat. |
[79] This specimen has been inadvertently drawn with the base uppermost.
The stellate appearance on the upper part of the stem figured in [Lign. 15, fig. 1], is produced by the zone of leaves which surrounded the joint: this character is entirely distinct from the sheath of the Equisetum shown in [Lign. 12]. This specimen points out the importance of carefully examining and preserving the stone around fossil stems; had this precaution been lost sight of in this instance, no knowledge would have been obtained of this important botanical character. It is rarely that any traces of the roots remain; the fossil figured ([fig. 2]) is from the Foss. Flor. A beautiful example of the foliage of a species of Calamites is represented in [Lign. 59, fig. 2].
Upright stems of Calamites occur in the Coal formation near Pictou, in North America; and in one example a group of ten or twelve stems, covering an area of two square feet, sprung from one root.[80]
[80] Dawson, Geol. Proc. vol. vii. p. 195. See Sir C. Lyell's Travels in North America, vol. ii. p. 195.