34 PETRIFACTIONS AND THEIR TEACHINGS. CHAP. I. 



the uniformity of the imprints suggesting the idea of impres- 

 sions made by a seal. The stems vary from a few inches to 

 several feet in diameter, and attain a length of fifty or sixty 

 feet. They are often found erect, and uncompressed ; in 

 general, all vestiges of internal. structure are lost, the cylinder 

 of carbonized bark being filled up with clay or sand, and 

 giving rise to large cylindrical casts of stone, slightly im- 

 pressed with the longitudinal furrows and leaf-pits. A few 

 examples of silicified stems have been discovered, and by 

 sections, and a microscopical examination of these fossils, the 

 internal organization of these remarkable extinct types of 

 vegetation has been ascertained. The Sigillariee were tall 

 erect trees, with a regular and cylindrical stem, having no 

 side branches, but becoming dichotomous at the summit. 

 Their superficial bark was hard and durable, channelled longi- 

 tudinally, bearing leaf -scars that are of a rounded form above 

 and below, and angular at the sides, often oblong in relation 

 to the stem, and having three vascular pits, one central and 

 small, and two lateral of a larger size. The internal structure 

 bears most analogy to that of the Cycadese, and the foliage 

 consisted of long linear carinated leaves. The Sigillarise, 

 therefore, differ essentially from the arborescent crypto- 

 gamia, which they somewhat approach in having scalari- 

 form vascular tissue, symmetrical and regular leaf-scars, and 

 branchless trunks. More than fifty species have been deter- 

 mined. 1 



Sigillaria (or Sagenaria) caudata. Case O. On the front 

 of the middle shelf of this case, immediately above the label 

 Filicites there is a sandstone cast of an uncompressed Sigil- 

 laria, deeply imprinted with the cicatrices left by the petioles, 

 which is remarkable for the extraordinary sharpness of 

 the scars, and the geological position ascribed to it. It 

 was discovered (as I was informed by the Dean of West- 

 minster, when examining, with him the fossil plants in this 

 case) in the Greensand, which is the lowermost group of the 

 chalk formation. Now, as the Sigillarise are peculiar to the 

 carboniferous epoch, no other instance being known of any 

 vestiges of this tribe of vegetables in subsequent deposits, it is 



1 Figures of Sigillariae in "Wonders of Geology," p. 719 ; "Medals 

 of Creation," p. 129, PL V.; " Pictorial Atlas," PI. XIX., XX., XXIV. 



