CHAPTER L 



EVOLUTIONARY BEARINGS OF THE RESULTS 



A COMPARATIVE study of the Class of the Fihcales extending over nearly 

 half a centur)' affords some justification for stating how certain of its results 

 appear to the author to be related to evolutionary theory. It has been said 

 that the essence of Evolution is unbroken sequence, and in this respect the 

 Fflicales are not found wanting. From the earliest fossil records of the Coe- 

 nopteridaceae to the present day we may hold that Ferns have been Ferns: 

 and that those we see now living have been derived in continuous sequence 

 from pre-existent Ferns. The theme of this work has been evolutionary 

 progress within the Class thus early defined, rather than its ultimate 

 origin. 



The lines of enquiry into the progressive evolution of the Class have been 

 chiefly morphological, pursued by study of the external form and internal 

 structure of the adult: also by following the ontogen\-: while palaeontological 

 data, the evidence best fitted to indicate actual successions, has been accepted 

 as a valid check upon the results acquired from comparison. On the other 

 hand, though physiological and genetic experiment may be introduced to 

 illuminate the problem, this can only be carried out upon organisms now 

 living; hence it cannot safely be held as reconstructing evolutionary history: 

 it provides a basis for estimating the probability of earlier events rather than 

 a demonstration of them. Even Mendelian analysis conducted experimentally 

 has not given us the origin of species, as Bateson himself has admitted. Inter- 

 crossing acts as a distributing agency of characters, but it does not create them. 

 All of these methods of enquiry should be coordinated, and the student' 

 of Descent should be cognisant of them all : but Comparative Morphology, 

 checked by the positive facts of Palaeontology, must still be the chief founda- 

 tion on which to base phyletic conclusions. As Darwin said, it is "the most 

 interesting Department of Natural History, and it may be said to be its very 

 soul." Applying the results of Comparative Morphology, aided as above, to 

 the phyletic study of so circumscribed a Class as the Filicales, we may 

 expect not only to approach a Natural Classification of them, but also to 

 obtain some definite opinions which will illuminate the problem of Evolution 

 at large. 



The facts detailed in these three Volumes, summarised in Chapter XLIX, 

 have led to the general conclusion stated in its last paragraph. The Filicales 

 have been shown to comprise a skein of phyletic lines: the early origin of 



