MANTON: PTERIDOLOGY 315 



A detailed enumeration of the differences between TTolttum's scheme and 

 Copeland's was published by Ilolttum (1949), to whicli the reader is referred. 

 It is sufficient to say here that, of the two, Ilolttum 's scheme is the more ex- 

 plicitly phyletic, embodying a very great deal of the work outlined on previous 

 pages in his view of the nature of the primitive prototype of the Polypodiaceae. 

 In Holttum's view the genus Dennstaedtia conforms most nearly to the hypo- 

 thetical primitive ancestor of the great majority of "polypodiaceaeous" lepto- 

 sporangiate ferns, a view w'hich is very clearly expressed in his phyletic diagram 

 reproduced here (fig. 3) from the 1949 paper. It is perhaps of interest to con- 

 trast this with Bower's earlier scheme, which is here reproduced as figure 2. 

 That it is an improvement on this scheme in many particulars is already ap- 

 parent from the evidence of the latest considerable source of new facts, namely 

 that from chromosomes (cf. Manton, 1950), although it is too soon to say how 

 much further modification will be needed before a generally agreed arrange- 

 ment is reached. 



Summing up, we may say that while one of the most active growing points 

 in pteridophyte taxonomy at the close of the century in 1951 concerns the 

 modern ferns, this is only a stage in grafting the idea of evolution onto the 

 Pteridophyta, a process which has taken almost the whole century to effect. 

 During it, w^hole fields of knowledge, such as life histories, morphology, anat- 

 omy, cytology, and paleobotany, have had to be explored for their own sakes but 

 in the process have contributed facts and ideas which are of fundamental 

 importance, not merely for the Pteridophyta but for the whole of botany. 

 The work has been carried out in many countries, of which Germany, France, 

 Britain, America, Holland, Belgium, Norway, Denmark, and Sweden have been 

 quoted in a historical survey which can only touch on headlines without at- 

 tempting to exhaust the whole immense literature. Since, however, this account 

 has been prepared at the request of the California Academy of Sciences, it may 

 perhaps be of interest to record explicity the more important American con- 

 tributions. Though relatively few in number these have been of decisive im- 

 portance on several occasions. It would be invidious to list contemporary writ- 

 ers, but of those of an earlier date we may point to Farlow's discovery of 

 apogamy while on a visit to De Bary's laboratory (1874), the general influence 

 of Campbell's work, more especially regarding the primitive nature of the Eu- 

 sporangiatae (1890), and the anatomical views of Jeffrey (1897 et seq.) as three 

 noteworthy instances. But perhaps most important of all was the discovery of 

 Psilophyton by Dawson in Canada in 1859. 



LITERATURE CITED 



Arnold, C. A. 



1947. An Introduction to Palaeobotany. New York and London. 



Baby, A. de 



1858. t)ber die Keimung der Lycopodien. Ber. Natiirf. Ges. Freiburg. 1858:467-472. 



1877. Vergleichende Anatomie der Vegetationsorgane der Gefasspflanzen. 



1878. tJber apogame Fame und die Erscheinung der Apogamie im AUgemeinen. 



Bot. Zeit, 36:450-495. 

 1884. Comparative Anatomy of the Vegetative Organs of the Phanerogams and Ferns, 

 Eng. trans. Oxford. 



