20 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [May 2, 



Fig. 2 shows the last-described specimen of Stigmaria of the 

 natural size, as it appeared when it was first cleared from its cover- 

 ing of pyrites ; Fig. 3 the central axis in its proper position, but 

 magnified twice. The small unshaded dots represent the detached 

 spores found equally scattered throughout the whole mass of the clay 

 ironstone forming the portion of the specimen between the vascular 

 axis and the bark. The central part formerly occupied by the pith 

 is also composed of clay ironstone, mixed with a little white spar. 

 The vascular axis, like the exterior of the fossil, is formed of iron 

 pyrites, showing the structure most beautifully. 



Fig. 4 represents the opposite 

 sides of three diiferent detached Fig. 4. 



spores taken from the inside of the 

 Stigmaria, out of the clay ironstone 

 in which they were imbedded. 

 They are larger than the average 

 size of the specimens found, and 

 show the raised divisions more di- 

 stinctly. Each of these drawings 

 is ten times the diameter of the 

 original specimen. 



That part of the Stigmaria which intervened between the vascular 

 axis and the bark appears to have consisted of two different kinds of 

 cellular tissue. These have in most cases been unfortunately de- 

 stroyed, so that we cannot positively know their true nature ; but 

 they appear to have been of different characters, for there generally 

 appears to be a well-marked division. This is often shown in speci- 

 mens composed of clay ironstone which have not been flattened, and 

 the boundary line is generally about a quarter of an inch from the 

 outside of the specimen. Most probably the outer zone has been 

 composed of stronger tissue than the inner one, as is the case with 

 well-preserved specimens of Lepidodendron. 



In my first paper on Stigmaria, published in vol. xxiv. page 165, 

 of the 'Philosophical Magazine,' I alluded to something like a tap root 

 having been seen, in the following words : " Immediately under, but 

 I could not see it join the tree, proceeded a stem like a tap root, 

 about 2y inches in diameter, inclining a little to the north ; it was 

 about two feet long, but owing to my being able only to examine the 

 mould, I could not make out its characters." As I could not trace 

 its absolute connexion with the tree above, I thought it possibly might 

 be a Calamites in situ. The late Mr. Bowman and myself carefully 

 examined the Dixon Fold fossil trees for the express purpose of disco- 

 vering tap roots to them, but we there found no satisfactory evidence 

 of any such appendage. I have since seen, in the Pemberton Hill 

 cutting on the Bury and Liverpool Railway, many stems of Cala- 

 mites standing erect in situ, both over and under many Sigillarise in 

 similar positions, but in no instance have I seen any example of what 

 I could consider a true tap root to Sigillaria. 



The crucial sutures on the base of Sigillaria alluded to by Dr. J. 

 Hooker, at page 417, vol. ii. of the 'Memoirs of the Geological Sur- 



