mer is terns of Ferns as a Phylogenetic Study. 359 
(1) That the leaves of the large majority of Ferns are 
winged, and that the wings may be traced, more or less 
distinctly, as continuous from the apex to the base of the leaf. 
(2) That the wings are typically delicate and thin in the 
Hymenophyllaceae, that those of the Polypodiaceae are more 
robust, while in the Osmundaceae (excluding the filmy Todeas ) 
and Marattiaceae the wings are thick and almost coriaceous. 
(3) That the type of the Hymenophyllaceae is that each cell 
of the marginal series has the form of half a disc, and the 
segmentation is transverse (Fig. 47) : in the Polypodiaceae the 
form of the marginal cell is a sector of a disc, and the seg- 
mentation is alternately from the upper and lower margins 
(Fig. 56) : that in the Osmundaceae (excluding the filmy 
Todeas ) and Marattiaceae there is no marginal series, but the 
cells forming the wing have square bases, and undergo a T 
division (Figs. 60, 72). 
(4) That the Hymenophyllaceae, Polypodiaceae and other 
leptosporangiate Ferns, Osmundaceae, and Marattiaceae form 
a natural series as regards the complexity of structure of the 
young wing, the first-named being the simplest, and the last 
the most complex. 
(5) That as we rise in this series, the centre of construction 
becomes more and more deeply seated, the progression in this 
respect being closely comparable to that above noted for the 
apical meristems of root, stem, and leaf. 
(6) That in the Ferns observed (and it may be stated also 
for Ferns generally) the wing is of a more robust character 
near to the base of the frond than in its upper portions, there 
being thus some relation of bulk of the wing to that of the 
phyllopodium which bears it. 
(7) That the wings may undergo various metamorphoses, 
being in some parts reduced, so as to be barely recognisable 
(petiole), in other parts being developed as broad flanges, or 
as the massive ‘ stipules.’ 
(8) That the ‘ filmy 5 character which depends upon thinness 
of the wings, and absence of stomata and intercellular spaces, 
is found to occur at three distinct points in the series, and 
