510 Bower.—Studies in the Phytogeny of the Filicales. 
circle (iii-iv, v-vi, vii-viii). From this circle come off at intervals strands 
of varying size, right and left. A comparison of Text-fig. io, i-xiii, illustrates 
the method, and the way in which these spread, with further branchings 
and fusions, to form the reticulum of the flattened wings. As these wings 
expand upwards, the midrib gradually diminishes, and its strands simplify 
in number and arrangement, till with final fusions of abaxial and adaxial 
strands (xii) the circle is reduced to a single plane. After this the reticu¬ 
lum follows the course easily seen from the surface view. There is some 
similarity between this arrangement and what is seen in Ophioglossum 
palmatum , in the fact that in both there is a circle of strands, with fusions 
across the frontal face. But the correspondence does not extend into detail, 
and there is no correlative in Ophioglossum for the antero-posterior fusion of 
the strands of the circle itself seen in Platycerium . The facts point to an 
interesting homoplasy in two quite distinct epiphytic types. 
The Sporophyll in Matonia , Dipteris , Cheiropleuria , AND 
Platycerium. 
A comparative examination will now be made of the venation of the 
sporophylls in the Ferns in question, and its relation to their soral develop¬ 
ments. It will be found that they form in 
a general sense a series, leading from simpler 
to more complex states ; and that so far as 
this comparison is concerned, they form a 
rough sequence in the order in which they 
have been named in the above heading. 
The venation of the fertile leaf of Matonia 
is known from the observations of Seward 
(Phil. Trans., vol. 191, Series B, p. 175, 
PI. 18, Fig. 23). The pinnules have a mid¬ 
rib, from which veins come off at a wide 
angle. They show frequent, but irregular 
anastomoses. But the most notable of these, 
as they are also the most regular, are those associated with the isolated 
sori. Each of the latter is seated at the centre of an areola formed by 
the lateral fusion of veins, while branches run radially in to the centre, 
where the receptacle is attached. At the base of the receptacle a few 
tracheides may be seen, but they do not extend conspicuously into it 
(Text-fig. 11). 
The condition of the fertile leaf of Dipteris is also known from the 
description given by Seward and Dale (Phil. Trans., Series B, vol. 194. 
See also Land Flora, Figs. 344-6). In D. Lohbiana the bifurcating lamina 
is narrower, and the sori are arranged in a more or less regular single row 
on each side of the midrib, as in Gleichenia . The venation is reticulate, 
Text-fig. ii. Portion of a 
pinna of Matonia to show the vena¬ 
tion, and its relation to the sorus. 
X 6. 
