78 
The apical cells are longer than those of the Polypodiaceze, 
but closely resemble them. (Fig. 9, 10). The segments are cut 
off from the base in the same way, and the first wall in the 
segment also divides it into two nearly equal cells, dorsal and 
ventral. The subsequent divisions, at least in the younger pro- 
thallia, are less regular and there is a preponderance of horizon- 
tal walls. (Figs. 9, 10). The difference in the rapidity of cell- 
division in the dorsal and ventral segments is not noticeable. 
How this may be in the older prothallia, and what the relation of 
the archegonia to the segments is, I cannot yet state, but hope 
‘soon to have an opportunity of examining this point carefully. 
When we compare the longitudinal sections of the prothallia 
with those of the liverworts, we find that most of the latter differ 
in one marked respect—viz: that two sets of segments are cut off 
from each apical cell (when seen in vertical section), a dorsal and 
a ventral one. This seems to be the case in all Marchantiacez* 
and Ricciacezet, and in Anthocerost; but in Dendroceros§, a near 
relative of the latter, we meet with exactly the same form as in 
the ferns (Fig. 11); and the single apical cell of Pellia epiphylla,|| 
according to Leitgeb’s account is also of the same type, although 
the nearly related P. calycinag has an apical cell closely re- 
sembling in its method of growth the individual apical cells of the 
Marchantiacez, and according to Hofmeister°, P. epiphyl/a in its 
earlier stages has the apical cell of the same form, so that the two 
types must be regarded asclosely related, and possibly interchange- 
able. It is by no means unlikely that further investigation will 
show both types in the ferns. 
Finally, the independent vegetative existence of the fern-pro- 
thallia, and the power of multiplication by branching are charac- 
ters which they have in common with the liverworts, and this is 
especially marked in the Osmundacez, Gleicheniacee and 
Marattiacez, just those groups which in other respects ap- 
mde So 
ai, ¢. 
mae c. 
§ Leitgeb, 1. c. Vol. V. p. 30. Pl. IL. 
| l. c. Vol. III. p. 6. 53. 
Wicd, VOL U1. pF. 53; 
° Hofmeister, The Higher Cryptogamia p. 23. Pl. IV. 
. 
