1 14 Bower . — Is Eusporangiate or Leptosporangiate 
Moss. But there are still further reasons for thinking this 
comparison unsatisfactory. I have attempted elsewhere to 
show that the £ filmy ’ texture of the leaf is not a safe indi- 
cation of close affinity even among the Ferns 1 , by pointing 
out that within the Filicineous series it occurs at three distinct 
points, viz. among the Hymenophyllaceae, the Aspleniums, 
and the Todeas : if within the very natural group of the Ferns 
themselves it is not a certain index of affinity, but is rather to 
be viewed as a result of direct adaptation, how can the filmy 
texture of the leaf be held to strengthen the comparison be- 
tween the Hymenophyllaceae and the systematically far distant 
series of the Mosses ? If the affinity be a true one, the evidence 
of it must be based on firmer ground than that of the filmy 
leaf 2 . 
(ii) The existence of a filamentous, protonema-like prothal- 
lus in the Hymenophyllaceae, affords what is apparently 
a better ground for comparison. Various writers have recog- 
nised its counterpart in the protonema of the Moss, but none 
has treated the matter so fully as Goebel, who has made a 
comparative study of the sexual generation of certain Ferns, 
and based upon it views as to the phylogeny of Mosses and 
Ferns, and the relationship between them : he sums up in the 
following words 3 : ‘We may accordingly regard as the starting- 
point of the Bryophyta and Pteridophyta, Alga-like forms, 
consisting of branched filaments, of which the female sexual 
organs produced on fertilisation the asexual generation. Even 
now we can partially trace ...... the phylogenetic develop- 
ment of the sexual generation, or at least form for ourselves 
a connected idea of it. Still it is not to be forgotten that 
besides the onward progress from the simple condition of 
1 Annals of Botany, vol. Ill, p. 379. 
3 Giesenhagen (Flora, Oct. 1890, p. 460) has cited the case of Selaginella 
euspidata as having at the margins of the leaf a texture similar to that of the 
Hymenophyllaceae, also Lycopodium linifolium , which is a shade-loving species. 
He concludes (p. 462) that the simplest Hymenophyllaceae were derived from 
forms of more complex construction, and are the result of progressive simplifi- 
cation of morphological structure : also that the Hymenophyllaceae are as near 
to the Polypodiaceae as any other family of homosporous Leptosporangiates. 
8 1. c., p. 1 15. 
