208 



DE. AGNES AEBEE ON THE 



with otliers which we know only as impressions. It is prohable, for instance^ that 



■m 



Lepidostrobus oldhamiiis may be identical with the cone-impressions known as 

 L. variabilis, LindL & Hutt., which are so common in the Coal Measures, Generally, 

 however, it is extremely difficult to correlate " impressions " and " petrifactions " of 

 cones. Several reasons for this difficulty readily suggest themselves. The features, 

 about which we obtain most information from petrified material, are the anatomy of the 

 axis and of the sporophylls, and the internal structure of the sporangium. The general 

 shape and dimensions of such cones are often imperfectly known, and the external form 

 of the sporophylls and sporangia is frequently difficult to reconstruct. In " impressions " 

 of cones, on the other band, it is just these external features about which information 

 is easiest to obtain, w^hile such material gives little clue to those characters which we 

 know in the greatest detail from petrified fructifications. 



Another cause of difficulty in correlation appears to be that the cones of these 

 species, which lend themselves most readily to entire or partial survival as impressions, 

 are often ill-adapted to preservation as petrifactions. We occasionally find, in the Coal 

 Measures, impressions of extremely large, detached sporophylls of Lepidostrobus. There 

 is, for example, a specimen in the Sedgwick Museum * in which the lamina reaches the 



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length of 8"9 cms. It seems obvious that a cone protected by the overlapping lobes of 

 such sporophylls would prove highly resistant to the infiltration of any petrifying 

 material. This may perhaps explain why it is that none of the cones with well-preserved 

 internal structure which have been described from the Coal Measures, possess sporo- 

 phylls approaching these dimensions. 



In a later section of this paper some account is given of certain forms of Lepidosti^obus 

 which do not appear to have been hitherto described. In none of these cases is it at 

 present possible to correlate the petrified cone with the stem which bore it, or with 

 impressions showing surface features. 



3. On CERTAIf^ HITHERTO UNRECORDED FEATURES IN THE STRUCTURE OF 



Lefidosteobus oldhamius, AYill., and L. foliaceus, Maslen. 

 (i.) The Existence of a Ste7^ile 'Plate in the Sporangium ofjj. oldhamius and 



L. EOLIACEUS. 



The type sections of Williamson's species, L. oldhamius, consist, as Maslen t 

 has pointed out, of two slides now in the Wilhamson Collection, British Museum 

 (C.N. 568 & 574) ; iu addition there are certain slides in the Binney Collection, 

 Sedgwick Museum, Cambridge, which were cut from the same cone. Sections of 

 another cone in the Williamson Collection, known as " Wild's Cone " (C.N. 1776 A & BJ, 

 are also attributed by Maslen to the type form. The preparations of the latter cone are 



• LtpidopliyVum majut^ Brongn. From the Tpper Coal Measures, Coal Pit Heath Colliery, near Bristol 

 Sedgwick Museum Coll., 2076. 

 t Maslen, A. J. ('99), p. 359. 



