Ch. XXIV.] 



CONIFERS OF THE COAL PERIOD. 



477 



or partial absorption of the original medullary axis (see figs. 531 and 

 532). This peculiar type of pith is observed in living plants of very 

 different families, such as the common Walnut and the White Jas- 

 mine, in which the pith becomes so reduced as simply to form a thin 

 lining of the medullary cavity, across which transverse 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 provisional name of Sternbergia (d, d, fig. 531) was given. 



In the above specimen the structure of the wood (6, figs. 531 and 

 532) is coniferous, and the fossil is referable to Endlicher's fossil genus 

 Dadoxylon. 



The fossil named Trigonocarpon (figs. 553 and 554), formerly sup- 

 posed to be the fruit of a palm, may now, according to Dr. Hooker, be 

 referred, like the Sternbergia, to the Coniferce. Its geological im- 

 portance is great, for so abundant is it in the Coal-Measures, that in 

 certain localities the fruit of some species may be procured by the 

 bushel ; nor is there auy part of the formation where they do not 

 occur, except the underclays and limestone. The sandstone, iron- 

 stone, shales, and coal itself, all contain them. Mr. Binney has at 

 length found in the clay-ironstone at Lancashire several specimens dis- 

 playing structure, and from these, says Dr. Hooker, we learn that the 

 Trigonccarpon belonged to that large section of existing coniferous 

 plants which bear fleshy solitary fruits, and not cones. It resembled 

 very closely the fruit of the Chinese genus Salisburia, one of the Yew 

 tribe, or Taxoid conifers. In five of the fossil specimens there is evi- 



Fig. 534. 



Fig. 533. 



Trigonocarpum ovatum, Lindley and Hutton. 

 Peel Quarry, Lancashire. 



Trigonocarpum olivafvrme, Lindley, 

 its fleshy envelope. Felling Col- 

 liery, Newcastle. 



dence of four distinct integuments, and of a large internal cavity filled 

 with carbonate of lime and magnesia, and probably once occupied by 

 the albumen and embryo of the seed. The general form of the fossil 

 when perfect is an elongated ovoid, rather larger than a hazel-nut. The 

 exterior integument is very thick and cellular, and was no doubt once 

 fleshy (see fig. 534). It alone is produced beyond the seed, and forms 

 the beak. The second coat was thinner, but hard, and marked by 



