mer is terns of Ferns as a Phylogenetic Study. 321 
Longitudinal sections show that the apical cell, both of the 
main axis (Fig. 20) and of the axillary bud (Fig. 21), is pointed 
and rather deep : deeper in fact than is usual with the apical 
cells of the stems of most leptosporangiate Ferns ; this is how- 
ever to be put in relation with the flattened form of the apex, 
and Prantl’s figures 1 seem to indicate that it is not so in 
the slender forms. 
The rhizomes of the following species were also examined ; 
viz. Trichomanes reniforme , and Hymenophyllum caudiculata- 
tum and demissum : in each a three-sided pyramidal apical 
cell was found, but in the two last-named species the further 
subdivision of the segments was found to be less regular 
than in 7 >. reniforme or radicans. From these observations 
it appears that the rhizome of the Hymenophyllaceae corre- 
sponds, as regards the essential characters of its apex, to the 
structure of the apex of the stem in the large majority of 
other leptosporangiate Ferns. 
On the apex of the stem of other leptosporangiate Ferns I 
have little to add to the excellent observations of Klein. He 
seems, however, to have had little opportunity of examining 
the stems of Cytheaceae or Dicksonieae, and though he cites 
Dicksonia rubiginosa and Hypoderris Brownii in his list of 
plants employed, he does not figure either of them, or describe 
them in the text. As far as I am aware, no observations have 
hitherto been made on the structure of the apex of the stem 
of large and well-grown Tree-Ferns, and it would be reasonable 
to expect that the very large size of the stem might react upon 
the structure of its apex. Having collected, when in Ceylon, 
apical buds of large plants of Amphicosmia ( Hemitelia ) Walker ae, 
these were investigated with the following result : The apex 
of the stem is not very broad, and is slightly depressed, while 
the extreme apex rises from the hollow depression as a central 
cone: this is terminated by a large and extremely well-defined 
three-sided pyramidal apical cell, from the sides of which 
successive segments are cut off ; these subdivide with consider- 
able regularity, and the character of the whole is quite as 
1 1. c., Plate I, Figs. 6, 9. 
