130 THE MEDALS OF CREATION. Cuap. VI. 
INTERNAL STRUCTURE OF SIGILLARIZ.—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 Bron- 
gniart. It has been described and illustrated by that emi- 
nent botanist, in a memoir which is one of the most valuable 
contributions to fossil botany that has hitherto appeared.” 
Lien. 35. SILICIFIED STEM OF SIGILLARIA ELEGANS. 
Autun. France. 
(M. Adolphe Brongniart.) 
Fig. 1.—A transverse section of the silicified stem, from Autun; zat. 
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. (x x.) 
3.—Portion of a spiral vessel of the same tissue. (x x.) 
The annexed figure (Zign. 35) is an outline of the speci- 
men, of the natural size ; but this sketch is a mere plan or 
* The reader intending to make fossil botany his particular study, 
should refer to the original memoir, and become familiar with the 
