SPHENOPHYLLEAE. 351 



were observed. The leaf-teeth, several of which are combined together in 

 the lower part of the stem, are enlarged in the middle and one-nerved, and 

 properly comparable with those of Sphenophyllum Stephanense. William- 

 son, on account of the deep incisions in these leaves which reach nearly 

 to the base, refers his specimen not to Sphenophyllum but to Astero- 

 phyllites, and tries to justify this by comparing the facts of the case with 

 the diagnoses of the two genera obtained from impressions. That such a 

 proceeding is inadmissible is evident from our remarks on p. 344 ; the 

 structure of the stem in this specimen is that observed in acknowledged 

 Sphenophyllae and only in them, and is sufficient to prove that it belongs 

 to that group. And if Stur l writes : ' As far as we know at present it is 

 the fact, that the Calamariae show as great differences of anatomical struc- 

 ture in the variously leaved branches of the same individual, as we are 

 accustomed to find in living vegetation even in different and very dissimilar 

 families,' it is simply from once more overvaluing the results obtained from 

 impressions. For who will venture to say that the supposed Asterophyllites, 

 from which the branches of Sphenophyllum grew, had not the same structure 

 as Sphenophyllum and was not simply a Sphenophyllum. 



Some account is also to be found in Renault 2 of the structural details 

 of the leaves, but unfortunately he does not say from which of his specimens 

 they are taken. The weak vascular bundles consist only of a few tracheides 

 combined into one strand, and surrounded by delicate bast-elements. Above 

 and between these are hypodermal fibre-strands. Van Tieghem 3 indeed 

 maintains that the bundles are diploxylous, like those of Cycadeae, but 

 Renault disputes this very decidedly. After seeing the preparations which 

 he was kind enough to demonstrate to me, I must declare myself to be 

 entirely of his opinion. Little is known of the attachment of the lateral 

 branches. No anatomical details are given of the only specimen figured by 

 Renault 4 ; it is a suspicious circumstance that there is no node to be seen 

 at the point of departure of the branch, though it may indeed have been 

 rubbed off. Hence the possibility that this fragment may come from a 

 triarch root is not to be ignored. Stur 5 too has his doubts. The root, 

 the structure of which appears in the transverse section supplied by Ren- 

 ault 6 , has a diarch primary strand in the form of a transversal line and 

 surrounded by secondary wood, which, though perfectly uniform all round, 

 presents in other respects the structure of the stem of Sphenophyllum. 

 Hence we can hardly have any doubt about the true character of this object. 



It remains only to examine the fructifications. These appear chiefly 

 in the form of cylindrical spikes with close resemblance in habit to those of 

 Calamariae, and have been repeatedly found as lateral ramifications of leafy 



1 Stur (10), p. 328. 2 Renault (2), vol. iv, Introd. p. 16, t. B. 3 van Tieghem (3), p. 173. 

 Renault (16\ t. I, f. 3. 5 Stur (9), p. 16. 6 Renault ;2), vol. iv. t. B, f. 2. 



