The Present Position of Palaeozoic Botany. 177 



B. PTEROPSIDA. 



V. Filicales. 



There is no part of Fossil Botany in which there have been 

 such revolution ar}- changes within a very sliort period as in the 

 question of the position of Palaeozoic Ferns. Till within the last 

 three years the Ferns were universally regarded as forming one of 

 the dominant classes of Palaeozoic plants — in fact, the most dominant 

 of all — and this estimate of their importance will be found in all 

 the Text-books. According to the computations of systematists the 

 Ferns constituted almost exactly one half ^) of the known Carboniferous 

 flora. The position has now so completely changed, that Prof. Zeiller, 

 than whom there is no higher authoritj'. wrote, in August of last 

 year, that the Ferns of the Palaeozoic period, though "they were 

 probably not entirely absent, occupied an altogether subordinate 

 rank".-) 



The ground for the radical change of view which Prof. Zeiller's 

 words indicate, is. of course, to be found in the recognition of the 

 Pteridosperms, a class of seed-bearing plants, to which, as it now 

 appears, the great majority of the supposed Palaeozoic Ferns belonged. 

 Prof. Zeillcr further points out that the reduction in the number 

 of true Ferns becomes more marked the earliei- the period to which 

 we go back: the Westphalian Flora is already less rich in true 

 Ferns than the Stephanian, and one may almost raise the question 

 whether, in the epochs of the Culm and the Devonian. Ferns really 

 existed (1. c. p. 726). These are very serious statements, but the 

 learned palaeontologist of the École des Mines is not alone in the 

 view he takes of the position. Mr. K i d s t o n , writing a few months 

 later ^) finds no evidence of "true Ferns'' below the Middle Coal- 

 Measures*], and comes to the conclusion that the Cjxadofilices 

 (Pteridosperms) "long antedated the advent of true Ferns". It may be 

 pointed out, however, that under the name "true Ferns" Mr. Kid s ton 



^) 250 out of 500 species according to Brongniart, Tableau des Genres de 

 Végétaux fossiles, 1849; 160 out of 330, according to a more recent enumeration by- 

 Kids ton, confined to the British Carboniferous Flora — Divisions of British Carboni- 

 ferous Eocks, Proc. R. Phys. Soc. Edinburgh, XII (1893—4). 



-) Zeiller, Une Nouvelle Classe de Gymnospermes: les Ptéridospermes, Rev. 

 Générale des Sciences. Ißme Année, Aug. 30, 1905. 



^) On the Microsporangia of the Pteridosperms. Abstract. Proc. Royal Soc. B., 

 Vol. 77, p. 161 (Jan. 6, 1906). 



*) "Westphalian" of Mr. Kidstou, who uses this term iu a narrower sense 

 than Prof. Zeiller, with whom it includes the Lower Coal-Measures also. 

 Progressus rei botanicae I. 12 



