496 FILICALES 
and finally by contraction of the whole Lycopod’ strobilas 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 
LLymenophyllum was held to correspond to the opened capsule! 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 
have been a general factor in the process. 
The revolt against this position was initiated by Campbell,? 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 Palaedzoic 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.2 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 Hymenophyllaceen, Leipzig, 1875. 
? Bot. Gaz., Jan. 1890, and Dec. 1891. See also Bower, Ann. of Bot., 1891, p. 127. 
3 Ann, of Bot., 1889, p. 305, and 1891, p. 127. 
