474 



SIGILLAEIA. 



[Ch. XXIV. 



Asterophyllites many vegetable fragments have been grouped which 

 probably belong to different genera. They have, in short, no charac- 

 ter in common, except that of possessing narrow, verticillate, one- 

 ribbed leaves. Dr. Newberry, of Ohio, has discovered in the coal of 

 that country fossil stems which in their upper part bear wedge-shaped 

 leaves, corresponding to Sphenophyllum, while below the leaves are 

 stalk-like and capillary, and would have been called Asterophyllites if 

 found detached. From this he infers that Sphenophyllum was an 

 aquatic plant, the superior and floating leaves of which were broad, 

 and possessed a compound nervation, while the inferior or submersed 

 leaves were linear and one-ribbed. " This supposition," he adds, " is 

 further strengthened by the extreme length and tenuity of the branches 

 of this apparently herbaceous plant, which would seem to have re- 

 quired the support of a denser medium than air." * 



Sigillaria. — A large portion of the trees of the Carboniferous pe- 

 riod belonged to this genus, of which about thirty-five species are 

 known. The structure, both internal and external, was very pecu- 

 liar, and, with reference to existing types, very anomalous. They 

 were formerly referred, by M. Ad. Brongniart, to ferns, which they 

 resemble in the scalariform texture of their vessels, and, in some de- 

 gree, in the form of the cicatrices left by the base of the leaf-stalks 

 which have fallen off (see fig. 527). But 

 with these points of analogy to cryptoga- 

 mia, they combine an internal organization 

 much resembling that of cycads, and some 

 of them are ascertained to have had long 

 linear leaves, quite unlike those of ferns. 

 They grew to a great height, from 30 to 

 60, or even 70 feet, with regular cylindri- 

 cal stems, and without branches, although 

 some species were dichotomous towards 

 the top. Their fluted trunks, from 1 to 5 

 feet in diameter, appear to have decayed 

 more rapidly in the interior than exter- 

 nally, so that they became hollow when 

 standing ; and when thrown prostrate on 

 the mud, they were squeezed down and 

 flattened. Hence, we find the bark of the 

 two opposite sides (now converted into 

 bright shining coal) to constitute two horizontal layers, one upon the 

 other, half an inch, or an inch, in thickness. These same trunks, 

 when they are placed obliquely or vertically to the planes of stratifi- 

 cation, retain their original rounded form, and are uncompressed, the 

 cylinder of bark having been filled with sand, which now affords a 

 cast of the interior. 



Sigillaria laevigata, Brong 



* Annals of Science, Cleveland, Ohio, 1853, p. 97. 



