236 LEPIDODENDREAE. 



median keel (Fig. 25 D}. It is only in a few authors that we find more 

 than a superficial notice of these Lepidophylla, which were usually taken, 

 even by O. Feistmantel \ for example, and by Stur 2 , for vegetative leaves, 

 but were recognised as sporophylls by Goldenberg and Schimper. Even 

 good figures are scarce, those especially which show the base of the leaf 

 attached to the lamina; some examples will be found in Goldenberg 3 , 

 O. Feistmantel 4 , Lesquereux 5 and Schimper 6 , and also in Geinitz 7 . The 

 large forms with obtuse terminations- to the laminae evidently belong to 

 cones of gigantic size, and agree in habit with those figured by Lesquereux 

 in the fructification mentioned above which he classes with Lepidophloios ; 

 they occur abundantly with remains of stems of that genus in the neighbour- 

 hood of Saarbriicken, and may be peculiar to it. 



All the facts which we have been discussing hitherto, and which are to 

 be observed in the impressions of our plants, are entirely confirmed by the 

 examination of silicified specimens ; but it is from the latter only that we 

 have obtained a complete knowledge of the spores which are contained in 

 the sporangia, and which could only be studied exceptionally and imper- 

 fectly in impressions. The most important point is, that heterospory, such 

 as that of Selaginella, has been distinctly ascertained in several individuals 

 of Lepidostrobus. But we must be careful not to draw any general con- 

 clusion from this fact, since there may have been isosporous and hetero- 

 sporous families with the same habit among Lepidodendreae, as there 

 are in Lycopodiae and Selaginellae in our recent vegetation. We are 

 in possession of a number of cones which apparently contain only one 

 kind of spores, but these are only fragments of a larger or smaller size. It 

 might be just in the part that is wanting that the other spore-form may 

 have been contained, and the suspicion is the more reasonable because in 

 our Selaginellae, as we know, the macrospores are often confined to a small 

 space at the base of the cone, in Selaginella spinulosa to the lowest sporo- 

 phyll. And even if a perfect cone were ever found with spores of only one 

 kind, it might still be objected that the other kind may have been confined 

 to different cones on the same plant ; it is true that this arrangement does 

 not occur at the present day, but this seems to be no reason why it may 

 not have occurred in former ages. But though we cannot expect that this 

 question will ever be certainly determined, yet it will be convenient to 

 speak generally of macrospores and microspores, as in well-ascertained 

 examples of heterospory, and to include under the word microspores those 

 cases also in which, as we know of no other kind of spores, there may 

 have been isosporous as well as heterosporous forms. We will now 



1 O. Feistmantel (3). 3 Stur (5). 3 Goldenberg (1), t. 15, f. 5 and t. 16, ff. 11-13. 



4 O. Feistmantel (3), t. 42. 5 Lesquereux (1), vols. i, ii, t. 69. ' Schimper (1), t. 61 



1 Geinitz (5), t. 2. 



