$50 FILICALES 
ancestor. If the attempt be made to sketch the characters of that ancestry 
they would be as follows: Probably like other primitive Ferns the early 
Schizaeaceae had an upright, dichotomously branching stock (retained until 
after the leading soral characters were established), with radially disposed 
leaves, which also branched dichotomously: a protostelic structure (retained 
till after Zygodium had assumed its creeping habit), and a relatively simple 
leaf, as indicated by the single strand of the leaf-trace. On the surfaces were 
simple filamentous hairs. The monangial sori were probably superficial, as 
indicated by Senfrendergia and Kiukia, with a tendency towards the margin 
realised in the more modern forms. The sporangia were relatively large, 
with the annulus consisting of more than a single series of cells. 
Of the living forms Zygodium represents structurally the most primitive 
type, being protostelic. Subsequently the stele dilated, perhaps to accommo- 
date the enlarging leaf-traces,! as seen in the genus Schzzaea; and became 
even dialystelic, as in Anedmia and Mohria; but the section Aneimtorrhiza 
probably assumed its prone habit before the solenostele became dialystelic. 
On this view Aveimia and AMohria would be anatomically the most advanced 
types. This harmonises with the facts relating to spore-output: for on this 
ground also Lygodiwum would be the most primitive, and the other genera 
would have proceeded further towards reduction in number of the sporo- 
genous cells. It is in Lygodium also that Zeiller recognised that more 
complex structure of the annulus which corresponds to that of the earlier 
fossils. 
There is, however, another, and from its entire independence of the 
characters compared above, a most important feature, which marks off 
Anetmia and Mohria as advanced genera in the family. Heim,? in 
selecting organs which are typical for the divisions of the Ferns and 
recur under altered cultural conditions, lays great stress upon the structure 
and mode of dehiscerfce of the antheridium, of which he recognises two 
types: Type A, in which at maturity the cap-cell breaks away ; this includes 
the Osmundaceae, Gleicheniaceae, Hymenophyllaceae, Cyatheaceae, Dick- 
sonieae, and Lygodium ; it is, in fact, characteristic of those Ferns which are 
usually held as primitive. Type B, in which the antheridium has a star-like 
dehiscence, includes Ameimia and Mohria, and the whole body of the Poly- 
podiaceae : thus these genera share with the later and presumably derivative 
Ferns? a character by which they differ from Lygodiwm. Accordingly, on 
their anatomy, on their spore-output, and on the mode of dehiscence of the 
antheridium Aveimia and Mohria appear relatively advanced, and Lygodium, 
which itself goes back to the Cretaceous Period, is relatively primitive: 
Any converse view will have to meet not only one, but all of these 
lines of evidence. 
1Boodle, Ann. of Bot., 1903, p. 530. ? Flora, 1896, p. 329, etc. 
3 Heim notes also other characters of the gametophyte in which Amezmza and Mohria 
differ from Lygodium: so that the distinction is not based merely on the antheridial 
dehiscence, but is more general. 
