﻿STIGMARIA PICOIDES. 



143 



§ 4. The Specimen No. 45, Stigmaria ficoides. Plate XXIV, figs. 1 — 3. 



Pig. 1 (natural size) represents the exterior of a decorticated Stigmaria ficoides, found 

 by me on an old coal-pit hillock at Over Darwen, Lancashire. It is uncertain whether it 

 came from the " Gannister" or from the " Lower Port Mine" of the Lower Coal- 

 measures, as both those seams had been wrought in the pit. It occurred in a nodule of 

 rich clay-ironstone. The depressed areolae, with a little mammelon in the centre, 

 marked by a dark spot, as also the corrugated lines surrounding the areolae, are very 

 distinct, and a better specimen of Stigmaria ficoides, of small size, is not often met with, 

 as far as its exterior is concerned. 



The rootlet from which my sections were taken was imbedded in the outer radiating 

 cylinder, or inner bark, about half an inch in depth, and was originally one fourth of an 

 inch in diameter, but it had diminished one half, probably from the removal of its thick 

 carbonaceous exterior during the process of petrification. The remaining eighth of an 

 inch is, for the chief part, composed of crystallized matter, most probably silica ; and it is 

 only a small circular speck, about one thirtieth of an inch in diameter, in the centre of 

 the rootlet, that affords evidence of structure. 



Pig. 2 (magnified 90 diameters) is a transverse section of the small circular speck. 

 Its exterior consists of a ring of fine parenchymatous tissue, three or four cells in 

 breadth. This is surrounded by a space, four or five times the diameter of the ring above 

 named, in which no structure is apparent, the fine tissue formerly occupying it having 

 disappeared ; then in the centre there is a beautiful pear-shaped mass of vascular tissue, 

 one ninetieth of an inch in diameter, consisting of twenty-seven large vessels, of hexagonal, 

 pentagonal, and other shapes, and of a bundle of very minute nearly circular vessels at 

 the upper extremity. 



Pig. 3 (magnified 90 diameters) is not a straight section, being about half way 

 between a longitudinal and a transverse section ; but it clearly proves that the vascular 

 tubes on all their sides were marked with transverse striae, as described by Professor 

 Goeppert in 1841 ; but his specimen did not exhibit so many vessels, only eleven, and 

 was not in so good a state of preservation as the one here described. Dr. J. D. Hooker 

 also examined and described a similar specimen, but it was not very distinct. As none of 

 the rootlets thus described were traced to their exact position in the main root ; and as in 

 my first description in the ' Quarterly Journal of the Geol. Soc' no figure was given of 

 the Stigmaria in which the rootlet occurred, it has been considered desirable to again 

 describe the specimen and at greater length. 



