Internal Structure of Sigillariæ.—Our knowledge of the structure of this numerous tribe of plants, has received an important accession by the discovery of the silicified fragment of a stem, which, fortunately for the advancement of science, was placed at the disposal of M. Adolphe Brongniart. It has been described and illustrated by that eminent botanist, in a memoir which is one of the most valuable contributions to fossil botany that has hitherto appeared.[101]
[101] The reader intending to make fossil botany his particular study, should refer to the original memoir, and become familiar with the facts and inferences so admirably enunciated by the author; not only for the illustration of the structure of the tribe of plants under consideration, but as a valuable exemplification of the manner in which all such inquiries should be conducted. See Archives du Muséum d'Histoire Naturelle, tom. i. Paris, 1839.
Lign. 35. Silicified Stem of Sigillaria elegans.
Autun. France.
(M. Adolphe Brongniart.)
| Fig. | 1.— | A transverse section of the silicified stem, from Autun; nat. a. Situation of the medullary tissue, occupied by coloured silex. b. Zone composed of bundles of vessels, forming the woody tissue. c. Band of cellular tissue d. Space between the ligneous cylinder and the bark, with no evident structure, but originally occupied by the external cellular tissue. e. Zone of indistinct cellular substance. f. External cortical envelopment, or bark. |
| 2.— | Portion of one of the vessels of the medullary tissue, as seen in a longitudinal section, (× ×.) | |
| 3.— | Portion of a spiral vessel of the same tissue. (× ×.) |
The annexed figure ([Lign. 35]) is an outline of the specimen, of the natural size; but this sketch is a mere plan or diagram, for it is impossible without the aid of colour to convey a faithful idea of the original. The student should observe, that when mineral matter has permeated the stems of plants, the vascular tissue is often so well preserved, that one such specimen affords more important information, than hundreds of examples in which the form alone remains.
SIGILLARLA ELEGANS.