428 
ELEMENTS OF GEOLOGY. 
Fig. 468. the woody structure of some of them 
showing that they were allied to the 
Araucarian division of pines, more than 
to any of our common European firs. 
Some of their trunks exceeded forty-four 
feet in height. Many, if not all of them, 
seem to have ditfered from living Coni- 
fermm having large piths; for Professor 
Williamson has demonstrated the fossil 
of the coal-measures called Sternbergia 
to be the pith of these trees, or rather 
the cast of cavities formed by the shrink¬ 
ing or partial absorption of the original 
medullary axis (see Figs. 468,469). This 
peculiar type of pith is observed in living 
plants of very difierent families, such as 
the common Walnut and the White Jas¬ 
mine, in which the pith becomes so re¬ 
duced as simply to form a thin lining of 
the medullary cavity, across which trans¬ 
verse plates of pith extend horizontally, 
so as to divide the cylindrical hollow into 
discoid interspaces. When these interspaces have been filled 
up with inorganic matter, they constitute an axis to which, 
before their true nature was known, the pi'ovisional name of 
Fragment of coniferous 
wood, Dadoxylon, of 
End! icher, fractured lon¬ 
gitudinally ; from Coal- 
brook Dale. W.C. Wil¬ 
liamson.* 
a. Bark. b. Woody zone 
or fibre (pleureuchyma). 
c. Medulla or pith. d. 
Cast of hollow pith or 
“ Sternbergia.” 
Fig. 469. 
Magnified portion of Figure 468; transverse section. 
&, b. Woody fibre. c. Pith. e, e. Medullary rays. 
Bternhergia {d^ Fig. 468) was given. In the above speci¬ 
men the structure of the wood (^, Figs. 468 and 469) is conifer¬ 
ous, and the fossil is referable to Endlicher’s fossil genus Da¬ 
doxylon. 
The fossil named Trigonoearpon (Figs. 470 and 471), for¬ 
merly supposed to be the fruit of a palm, may now, according 
to Dr. Hooker, be referred, like the Sternbergia., to the Coni- 
ferce. Its geological importance is great, for so abundant is 
it in the coal-measures, that in certain localities the fruit of 
* Manchester Phil. Mem., vol. ix., 1851. 
