FLORA OF THE DEVONIAN. 



535 



size, being fully one-third larger in their diameter than those of Pinus 

 strobiis or Araucaria Gunninghami., and also much larger than those of 



Fig. 185. — Dadoxylon Ouangondianum. 



A B 



A, Fragment showing Sternbergia pitli and wood; (a) Medullary sheath; (i) Pith; (c) Wood; 



{il) Section of pith. 



B, Wood cell {a), and Hexagonal areole and ixire (b). 



C, Longitudinal section of wood, showing (o) Areolation, and (J) Medullary rays. 



D, Transverse section showing (a) Wood-cells, and (&) Limit of layer of growth. 



the ordinary coniferous trees of the Coal measures. They are beauti- 

 fully marked with contiguous hexagonal areoles, in which are inscribed 

 oval slits or pores, placed diagonally. The medullary rays are large 

 and frequent, but their cells, unlike the wood-cells [prosenchyma]^ are 

 more small and delicate than those of the trees just mentioned. The 

 pith when perfectly preserved presents a continuous cylinder of cellular 

 tissue, wrinkled longitudinally without, and transversely within, and 

 giving forth internally delicate transverse partitions, which coalesce 

 toward the centre, leaving there a series of lenticular spaces, a 

 peculiarity Avhich I have not heretofore observed in these Stern- 

 bergia pith cylinders. It is interesting to find in a Devonian conifer 

 the same structure of pith characteristic of some of its allies in the 

 Coal formation, where, however, as I have elsewhere shown,* such 

 structures occur in Sigillaria as well ; and since Corda has ascertained 

 a similar structure in Lomatojloyos^ a plant allied to Ulodendron, it 

 would appear that the Sternbergiaj may have belonged to plants of 

 very dissimilar organization. 



* Paper on Coal Structures. Journal of Gcol. Soc. 



