124 THE MEDALS OF CREATION. Cnap. VI. 
tints of blue and yellow, from the infiltrated chalcedony with 
which the vessels are permeated.* 
An excellent work (“ Dendrolithen”) on these fossils, in 
which thirty species are described, has been published at 
Dresden by M. Cotta ; who arranges them under the genus 
Psaronius or Psarolites. The stem is composed of two 
distinct parts ; an outer zone, consisting of a great number 
of nearly cylindrical bundles of vessels, supposed to have 
been roots which proceeded from the stem near its base ; and 
an inner part or axis. In the outer portion, the fossil az- 
roots have a vascular tissue, but there is often a delicate 
cellular tissue interposed. In the axis the vessels form zig- 
zag or wavy bands, resembling those of ferns. These flexuous 
and vermiform bands are entirely composed of barred or 
scalariform vessels, similar to those of ferns and club-mosses. 
The Psarolites are therefore considered by M. Ad. Brongniart 
to be the bases of the trunks of lycopodiaceous trees, 
while M. Cotta and other botanists regard them as true 
arborescent ferns. { 
Dr. Buckland has discovered in the New Red sandstone 
formation at Allesley, near Coventry, silicified trunks of 
coniferous trees, and it is not improbable that further 
research in that locality may bring to light fern-stems like 
those of Chemnitz.§ Dr. Lloyd, of Warwick, has recently 
obtained leaves of several coniferee from the same locality. || 
* See Pict. Atlas (pl. viii.) for coloured figures; and Org. Rem. 
vol. i. plate viii. fig, 1—7. The reader will be amused by the 
perusal of the ingenious but unsuccessful attempt of the excellent 
author, Mr. Parkinson, to elucidate their nature. I have still a speci- 
men which he presented to me more than thirty-five years since, 
as one of the most curious and perplexing fossils that had ever come 
under his notice. 
+ Pict. Atlas, pl. viii. 
~ See M. Brongniart’s “ Tableau des Genres de Végét. Foss.” p. 44. 
§ Vide Geol. Proc. vol. ii. p. 438. 
|| Geol. Society, June 1852. Dr. Lloyd’s specimens are probably 
referable to the genus Walchia : see Lign. 60. 
eT be ees Sites 
eres al 
oC aes 
