302 Sternhergi(t. 



inaica, I found the same structure ; and in the young branches, 

 before the central part of the pith was broken up, it was evident 

 that the tissue was of two distinct kinds — one forming the outer 

 coating and transverse partitions opposite the insertions of the 

 leaves, and retaining its vitality for several years at least ; the other 

 occupying the intervening spaces or internodes, of looser texture^ 

 speedily drying up, and ultimately disappearing, (Fig. 5j A.) 



Another variety of the Sternbergia-like pith structure appears 

 in a rapidly growing exogenous tree with opposite leaves, culti- 

 vated here, and I believe a species of Paullinia. In this trunk 

 there are thick nodal partitions, and the intervening spaces 

 are hollow and lined with firm corky pith, with its superficial 

 portion condensed into a sort of epidermis, and marked with trans- 

 verse wrinkles ; a cast of which would resemble these Sternbergiae 

 which have merely wrinkles without diaphragms. 



The trunks above noticed are of rapid growth, and have large 

 leaves ; and it is probable that the more permanent pith tissue of 

 the medullary lining and partitions, serves to equalize the distribu- 

 tion of the juices of the stem, which might otherwise be endan^ 

 gered by the tearing of the ordinary pith in the rapid elongation 

 of the internodes. A similar structure has evidently existed in 

 the coal formation conifers of the genus Dadoxylon, and possibly 

 they also were of rapid growth, and furnished with very large or 

 abundant leaves. 



I have no means of ascertaining to what extent this structure 

 may characterise certain botanical families, nor what gradations 

 it may present, between the mere transverse cracking observed 

 in the trunks of the Butternut and other Juglandacese, and the 

 perfect partitions developed in Cecropia. Prof. Gray states that 

 the transverse pith structure is characteristic of the North 

 American trees of the genus Juglans, but wanting in the closely 

 allied genus Carya — a parallel case with its apparent restriction to 

 one genus, or perhaps species, of extinct conifers. It is quite pos- 

 sible that some of the more rapidly growing and thicker-branched 

 species of southern conifers, still present similar structures. The 

 axes of cones also deserve study in this respect, since I have ob- 

 served that the pith of the cone of Pinus Strobus shows, though 

 obscurely, a tendency to the formation of transverse dissepiments. 



Applying the facts above stated to the different varieties or 

 species of sternbergia, we must in the first place connect with 

 these fossils such plants as the Pinites Medullaris of Witham. I 



