496 FILICALES 



and finally by contraction of the whole Lycopod strobilus the synangium 

 of the Psilotaceae. On the other hand, the origin of the simple Lepto- 

 sporangiate sporangium was traced on the theory of Prantl, through the 

 Hymenophyllaceae, directly from the Moss-sporogonium ; the sorus of 

 Hymenophyllum was held to correspond to the opened capsule. 1 These 

 were doubtless extreme opinions of the time, but they show the position 

 assigned to the Leptosporangiate Ferns in the discussions of a generation 

 ago. These plants were regarded as the primitive Pteridophytes, and other 

 forms as having been derived from them, while reduction was held to 

 luive been a general factor in the process. 



The revolt against this position was initiated by Campbell,' 2 who 

 definitely gave precedence to the Eusporangiate types. Over and above 

 the difficulties of comparison already felt, there loomed large the 

 impossibility of harmonising a belief in the Leptosporangiate Ferns as 

 primitive with the growing knowledge of Palaeophytology. The dearth 

 of evidence, even of the existence of true Leptosporangiates comparable 

 to those of the present day in Palaeozoic times, was pointed out : at 

 the same time the existence of numerous fossils then believed to be 

 rightly referred to the Marattiaceous affinity, indicated a priority of the 

 Eusporangiate type. The comparative study of development of the vegeta- 

 tive organs and of the sporangium had meanwhile been actively pursued : 

 on the basis of such facts it came to be held as probable that the more 

 delicate structure seen in the Leptosporangiate Ferns was not itself 

 primitive, but resulted from progressive specialisation. 3 With the adoption 

 of such a view the theories of Strasburger and of Prantl fell away, and 

 the ground was open for recognising the Eusporangiate type, whether of 

 Ferns or of other Pteridophytes, as of prior existence. 



As a consequence, the Marattiaceous type of Ferns was believed to 

 be the prevalent megaphyllous constituent of the Palaeozoic Flora. The 

 sporangial structure, as well as the construction of the sori in many forms, 

 agreed more or less nearly with that conclusion. The Lycopodiales, 

 Equisetales, and Sphenophyllales, however, were held to constitute separate 

 Eusporangiate phyla, there being no need to refer them to a Filicineous 

 origin. The next step affecting the early history of the Fern -phylum was 

 the discovery that certain of those fossils which had been held to be 

 true Ferns of the usual homosporous type were in reality Seed-bearing 

 Plants, the male sporangia of which had been taken for the fructifications 

 of a homosporous nature. The removal of such forms to the newly con- 

 stituted Class of Pteridosperms has perhaps only commenced, and it is 

 still impossible to say for certain how many of the fossils bearing like 

 fructifications may follow. The question is thus raised, what is the 

 residuum of true Ferns that actually remains among the Palaeozoic 



1 Die ffymenophyllaceen, Leipzig, 1875. 



2 Bot. Gas., Jan. 1890, and Dec. 1891. See also Bower, Ann. of Hot., 1891, p. 127. 



3 Ann. of Bot., 1889, p. 305, and 1891, p. 127. 



