670 



HISTORICAL GEOLOGY. 



One of the cones of a Lepidodendrid from Pittsburg, Pa., is represented 

 in Pig. 1039. 



The Stigmarice, which were either roots or under-water-stems of 

 Sigillarids or Lepidodendrids, were often large, many of the fossil stems 

 being four to six inches in diameter. Fig. 1041 represents a portion of a 

 stem, with its rounded impressions or scars. When perfect, each scar was 

 the base of a long and slender leaf -like appendage. 



1045-1048. 



Feens. — Fig. 10i5, Odontopteris ScMotheimi ; 1046, Alethopteris lonchitioa ; 104T, Sphenopteris (Hymeno- 

 phyllites) HOdrethi ; 1047 a, portion of the same, enlarged ; 1048, Sphenopteris Gravenhorstii ; 1048 a, portion 

 of the same, enlarged. Figs. 1045-1047, Lesquereux ; 1048, Brongniart. 



Ferns. — Two of the large scars of stems of Tree-ferns are shown in 

 Pigs. 1042, 1043 ; and, for comparison, one from a modern Tree-fern (resembling 

 the tree to the left in the sketch, page 666) is represented half-size in 

 Pig. 1044. The trunks of Tree-ferns consist within of vertically plicated 

 woody plates, with more or less cellular tissue between, and not of concentric 

 rings. The twisted plates are sometimes well shown in a transverse section 

 of a fossil trunk from the Coal-measures. 



The variety of Perns was very large. Some of the more common forms 



