On PaMavicinia decipiens , Mitten. , 41 
(Blyttid) Lyellii 1 , which was especially studied by him, and 
this fact affords another example of the marked dissimilarity 
of form and structure in the vegetative organs, which may 
exist in even allied species, and the difference described by 
Leitgeb 2 as existing between P. epiphyllo and P. calycina in 
the structure of their respective apices is another case in point. 
Division in the lateral segments takes place by means of 
walls which first cut the segment into an inner and an outer 
cell, and then, in the ordinary vegetative segments, a further 
wall parallel to the segment- wall appears. The further 
divisions were not studied. The apical cells of branches are 
formed very early, and are delimited by the first wall which 
appears in the segment, cutting off the inner from the outer 
cell. It is the latter which becomes the young apical cell of 
a lateral axis. 
The segments given off parallel to the inner face of the 
apical cell divide chiefly by longitudinal walls, and contribute 
to form the central strand of the rhizome, which has been 
described above. 
When the dormant resting apical cells of lateral branches 
are about to become active, walls appear in them which 
eventually cut out a cell similar to that which has already 
been described for the mother-apex. But the new walls are 
somewhat irregular at first (PL VI, Fig. 10), and it must be 
borne in mind that the cell in its dormant condition is in 
form a rectangular prism, which of course is a consequence of 
the way in which it originates in the young segment. The 
new walls then have to cut out a triangular prism, but it 
frequently happens that this is not effected until several 
divisions have occurred, and it is to this fact that the some- 
what irregular appearance as regards the arrangement of the 
cells at the new apex is to be attributed. 
One result of this lateness in the development of the 
branches is seen in a feature which was also noticed by 
Leitgeb in Pallavicinia {Blyttid) Lyellii , and doubtless the 
explanation is similar in both cases. The axile strand of 
1 Loc. cit. 
2 Loc. cit. 
