FERNS— FRONDS 273 



In some species of Sphenopteris the main rachis is 

 itself forked. These species, as well as Diplotmema, no 

 doubt represent the foliage of Pteridosperms, but some 

 other Sphenopterid fronds are known to have borne 

 fructifications referable in all probability to Ferns (e.g. 

 Oligocarpia, Corynepteris). 



It will, of course, be understood that there are many- 

 other form-genera to which Fern-like fronds are re- 

 ferred by systematists ; the enumeration of these would 

 serve no purpose here. Full accounts of the artificial 

 system of classification will be found in any of the 

 manuals of fossil botany. Some other types of frond 

 will be referred to in describing the Pteridosperms, for 

 in the majority, as mentioned above, the evidence, either 

 direct or indirect, indicates that the leaves in question 

 belonged to seed-bearing plants. The well-known 

 example of the recent Stangeria, which, when first 

 discovered, was referred to the Fern-genus Lomaria, 

 already showed plainly enough that Fern-like foliage 

 is not necessarily any proof of close affinity with 

 Filicineae. 1 



Before leaving the subject of the fossil Fern-like 

 fronds, we may briefly mention the curious stipellar 

 outgrowths, or adventitious pinnae, as they have been 

 called, which occur on the rachis of many of these 

 leaves, and . are usually known as Aphlebiae. These 

 bodies, when detached from the frond, have been 

 described as independent genera of Ferns, or even as 



1 It is now generally admitted that there is a real relationship between 

 the Cycadaceae (to which Stangeria belongs) and the Ferns, so that the 

 occasional resemblance in the leaf - characters is not wholly without 

 significance. The question is discussed at length in the following 

 chapters. 



