582 FILICALES 
Various fossil fructifications from early geological formations have been 
referred to the Hymenophyllaceae with more or less reason. The Devonian 
Palacopieris hibernica may be put aside as insufficiently known, while it 
shows no distinct evidence of Hymenophyllaceous affinity: moreover, the 
presence of its stipules is against it. In Aymenophyllites Weisstz, Sch., 
figured by Schimper from the coal of Saarbrucken, the reference is chiefly 
upon the sorus as a whole, while the sporangia themselves were not 
distinguished, or described in detail. Perhaps the best authenticated case 
is that of Aymenophyllites delicatulus (=H. quadridactylites (Gutb. Zeiller), 
described and figured by Zeiller.1 Here the sori were borne on the distal 
ends of the pinnules: he was also able to recognise and draw the sporangia, 
with an oblique annulus, which corresponds very closely with that of a 
modern Filmy Fern. The original specimens were examined by Solms- 
Laubach, who concluded that the fact is correctly stated, and no other 
interpretation of the figures is possible.? Scott, however, remarks® that 
the evidence as to the position of the reproductive organs on the leaf is 
not sufficient to place the affinities of these fossils beyond doubt. 
It must be admitted that the evidence of existence of Hymenophyllaceous 
fructifications from the Primary rocks is insufficient. It does not, however, 
appear essential to the position to be ascribed to the Hymenophyllaceae 
below that their early existence should be established, though their occurrence 
even in the primary rocks would readily accord with the view here enter- 
tained of their origin from the protostelic Simplices. 
ANATOmY.?* 
The most obvious structural peculiarity of the Hymenophyllaceae is the 
“filmy” texture of their leaves: the lateral wings throughout are pellucid 
owing to the absence of intercellular spaces, while there are no stomata 
upon them. Usually the flattened region consists of only a single layer of 
cells, though in some cases, such as Z. venifurme and A. dilatatum, 
there may be three or four layers, but still without intercellular spaces. 
The question naturally arises whether this filmy character is primitive or 
the result of special adaptation. In Prantl’s view it was held to be primitive, 
and indicated an affinity with the Mosses; but there are many reasons 
for rejecting this, and seeing in the simple structure a specialised and 
reduced character. It is plainly suited to the moist habitats in which the 
Hymenophyllaceae mostly live: while on the other hand quite a number 
of Ferns living in moist surroundings, but of divers affinity, show the same 
character in varying degree: it is seen in Danaea crispa, Endres, and in 
D. trichomanotdes, Spruce, MMS. ; but in these several layers of cells are 
present, with intercellular spaces: it is seen in various degrees in the 
Leptopierts section of Zodea, and most clearly in Z. superba: also in 
1 Ann. Sct. Nat., Ser. 6, vol. xvi. 2 Palaeophytology, p. 157. 3 Studies, p. 264. 
4See Boodle, Ann. of Bot., xiv., p. 455, where the literature is fully referred to. 
