FILICES. 133 



mode of branching of the whole leaf, and this course might be defended on 

 the ground that these differences are also employed as good subordinate 

 marks in dealing with living forms. But genera such as have been recently 

 founded by Stur 1 and Zeiller 2 (Diplotmema, Stur, Mariopteris, Zeill.), which 

 rest solely on the form of a leaf with one or two bifurcations, as in 

 Gleichenia, and contain species with different kinds of nervation, cannot 

 possibly find a place in any logical development of Brongniart's system. 

 And as their value is entirely relative so long as we have no proper know- 

 ledge of their fructifications, the gain resulting from their establishment, if 

 not altogether doubtful, must still be very small. 



It is obvious that we must remain in uncertainty with respect to the 

 configuration of the whole leaf in the many species which we know only in 

 single detached pinnules. Imperfect remains of this kind must simply be 

 entered under the names of the types of nervation to which they belong, 

 and which. are used as generic names, until further fortunate discoveries 

 teach us better. This proceeding is attended with an evil which is in some 

 cases unavoidable, namely that isolated pinnae of the same leaf are repeat- 

 edly and unconsciously registered under different names in different parts of 

 the system. A considerable number of leaves found in the Coal-measures 

 have in addition to the normal pinnules of the lamina of the leaf a second 

 kind of pinnae of another shape and often with an entirely different nervation 

 (Fig. 12), which grow in numbers either from the surface of the main rachis 

 or at the base of the rachides of the second order, or are confined to the 

 base of the leaf-stalk. These anomalous pinnae are now usually termed 

 Aphlebiae, but they are noticed in the literature under various names. The 

 same phenomenon occurs also, though rarely, in living Ferns ; I have myself 

 seen only two cases of the kind. The first is the well-known Hemitelia 

 capensis, R. Br., common in botanic gardens, in which two much-branched 

 Aphlebiae appear on each side of the base of the leaf-stalk ; a figure of this 

 species will be found in Schimper 3 . A second undetermined species, which 

 unfortunately has since died, I remember to have seen in the botanic garden 

 at Strassburg. A very excellent and complete account of these structures 

 has been given by Stur 4 , who compares them with the stipular formations 

 of the Marattiaceae, and inclines to the belief that every fossil fern-leaf 

 which bears these Aphlebiae must therefore belong to that family. I can- 

 not assent to this view, on account of the recent plants just mentioned 

 which bear Aphlebiae and belong to the family of Cyatheaceae. I now 

 give a list of all the figures which have come to my knowledge, which show 

 Aphlebiae in connection with the leaf which bears them. They are these : 

 (i) Sphenopteris crenata, Lindl. and Hutt., with the Aphlebia Rhacophyl- 



1 Stur (3), p. 283, and (4), p. 183. '' Zeiller (5) and (6\ :1 Schimper (2), p. 143. 



Stur (5), p. 195. 



