LEPIDODENDRON. 



/ / 



their own words ; but the facts observed by me are left to speak for or against such 

 views, without specially combating or supporting them. 



IV. Description of the Specimens. 



§ 1. The Specimen {Lepidodendron Harcourtii), No. 31. Plate XIII 

 (and No. 18, p. 48, Plate VII, fig. 6). 



For this beautiful fossil (PI. XIII, figs. 1 — 6) I am indebted to the kindness of my 

 friend Mr. J. S. Dawes, who discovered it in the clay-ironstone of the Coal-measures near 

 Dudley. The original specimen, however, from which the slices were made has unfor- 

 tunately been lost or mislaid ; but, from what we can learn, we understand that it 

 exhibited all the external characters of rhomboidal scars, and other appearances, which 

 generally distinguish L. Harcourtii. 



The transverse section of the specimen, magnified three and three quarters diameters, 

 in fig. 1, is irregularly oval, measuring one and a half inches across its major, and one 

 inch across its minor axis. The medulla is nearly circular, and measures two eighths of an 

 inch in diameter. For about one tenth of an inch within the circumference of the speci- 

 men there appears, for the greater part of the distance, a line of division, as if there had 

 been originally some change of structure there. 



The central axis is eccentric, as is generally found to be the case with specimens of 

 Lepidodendron affording evidence of the former existence of a medulla. It has been 

 considered that such displacement has arisen from the destruction of the cellular tissue 

 surrounding it ; but in this instance nearly the whole of the structure, from the centre to 

 the circumference, has been beautifully preserved ; and therefore the displacement of the 

 central axis in this instance can scarcely be attributed to that cause. 



The celebrated Hesley Heath specimen, so fully illustrated and described by Witham, 

 Lindley and Hutton, and Brongniart, and from which nearly the whole of our knowledge 

 of the structure of Lepidodendron has been obtained, was by no means in a good state of 

 preservation, so far as its medulla was concerned. This was assumed to consist of 

 common parenchymatous tissue, like that constituting the greater portion of the stem 

 exterior to the vascular cylinder. In the specimen now under description we shall find 

 that the medulla, as represented on a large scale in Plate VII, fig. 6, of Part II of this 

 Monograph, shows in a distinct manner every cell ; but these are not those of cellular 

 tissue, such as is usually found to constitute ordinary pith, but large oblong cells, 

 arranged in vertical series, exactly resembling those first described by Mr. Dawes as com- 

 posing the medulla of Halonia. In my description of Sigillaria vascularis} many years 



1 'Quart. Journ. Geol. Soc. London,' for May, 1862, vol. xviii, p. 106, pi. iv. 



