Ch. XXIV.] 



SIGILLARIA AND STIGMARIA. 



367 



cicatrices left by the base of the leaf-stalks which have fallen off (see 

 fio\ 480). But with these points of analogy to cryptogamia, they com- 

 Fj£r 4so. bine an internal organization much resembling 



that of Sycads, and some of them are ascer- 

 tained to have had long linear leaves, quite 

 unlike those of ferns. They grow to a great 

 height, from 30 to 60, or even 70 feet, with 

 regular cylindrical stems, and without branch- 

 es, 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 externally, 

 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 consti- 

 tute 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 stratification, 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. 



Dr. Hooker still inclines to the belief that the Sigillarice may have 

 been cryptogamous, though more highly developed than any flowerless 

 plants now living. The scalariform structure of their vessels agrees pre- 

 cisely with that of ferns. 



Stigmaria. — This fossil, the importance of which has already been 

 pointed out, was formerly conjectured to be an aquatic plant. It is now 

 ascertained to be the root of Sigillaria. The connection of the roots with 

 the stem, previously suspected, on botanical grounds, by Brongniart, was 

 first proved, by actual contact, in the Lancashire coal-field, by Mr. 

 Binney.' The fact has lately been shown, even more distinctly, by Mr. 

 Pdchard Brown, in his description of the Stigmarice occurring in the 



Fig. 481. 



Sigillaria laevigata, Brong. 



Stigmaria attached to a trunk of Sigillaria* 



* The trunk in this case is referred by Mr. Brown to Lepidodendron, but his 

 illustrations seem to show the usual markings assumed by Sigillaria near its 

 base. 



