Bower . — Studies in the Phytogeny of the Filicales . 3 1 1 
Discussion of the Phyletic Relations of the Ferns described above. 
Comparison has now been made between Lophosorict and those Ferns 
with which its relationship has habitually been recognized by earlier writers 
in respect of various leading characters, external and internal. The result 
has been in the first place to confirm on every count the recognition of its place 
at the base of the Cyatheaceous series, while the newly acquired facts have 
materially strengthened the relation of these Ferns with the Gleicheniaceae. 
It is not necessarily to be concluded that any present Cyatheaceae were 
directly derived from any Gleicheniaceous ancestors such as we now see 
them. What is concluded is that a stock of Ferns with the creeping habit, 
vascular structure, and soral characters essentially like those of the living 
Gleicheniaceae gave rise on the one hand to the Gleicheniaceae themselves, 
and on the other to the Cyatheaceae. 
Among the living species of Gleichenia , we have concluded that 
G . flabellata represents a central type, with its protostelic creeping axis, its 
deeply pinnate Mertensia- type of leaf, and its superficial, uniseriate sorus, 
of few, laxly-grouped sporangia, each with a large spore-output. A line of 
xerophytic specialization resulted in the En-Gleichenia section of the genus, 
still with protostelic axis, and with sorus of the same type, but with the 
ultimate pinnules much smaller, like shells concave downwards, protecting 
the sori. There is, moreover, a profuse protection of the young stems and 
leaves by scales, shared in less degree by G . flabellata ; this is probably 
a further sign of xerophytic adaptation. 
But another line of specialization was without these xerophytic signs, 
while it retains the more extended pinnule, and shows only hairs and no 
scales as dermal coverings. It is represented by G. linearis and G. pecti- 
nata . The former is anatomically and sorally the nearer to the central 
Mertensia-type. But G. pectinata shows complete solenostely, while it has 
been pointed out that its sorus had reached the practicable limit of elabora- 
tion, so long as the receptacle remains short, and the sporangium retains the 
distal dehiscence in a median plane. This circumstance probably blocked 
further progress of an otherwise successful line ; in fact, G. pectinata may be 
held to represent the ultimate realization of its own type. On this view, 
then, the Gleicheniaceae in their modern developments represent a blind 
evolutionary branch. 
But either an extension of the receptacle or a lateral dehiscence of the 
sporangium, or better, a combination of both these factors, would make 
further advance possible . 1 The latter only is realized in Lophosoria , but 
both are combined in the typical Cyatheaceae. All these Ferns have, 
however, the same position and general type of sorus as the Gleicheniaceae, 
1 A third possible factor would be an enlargement of area of the receptacle. This was probably 
realized in Metaxya , a Fern to be specially investigated later, together with other phyletic conse- 
quences believed to have eventuated along this line of advance. 
