442 Bower.—Studies in the Phytogeny of the Filicales . 
type may be held to be the more primitive ; the other is generally charac¬ 
teristic of the Polypodiaceae, together with Anemia and Mohria ; here 
the rupture is by breaking down of a distal cell, with the formation of 
a rosette-like aperture. The latter is the type seen in the antheridia of the 
prothalli attributed to Plagiogyria ; the process has been carefully watched ; 
first an increased convexity of the antheridial wall appears near to the distal 
end ; this gradually protrudes more and more, till rupture of the wall 
begins at one side of the cell; the convex part of the wall is then turned 
back as on a hinge, and the spermatozoids come out of the opening; there 
is no extrusion of a complete cell, but the wall of the distal cell is ruptured, 
and fragments of it remain attached to the antheridium, forming the star- 
like outline of the aperture. 
Comparisons. 
Comparisons may now be instituted between the characters of Plagio¬ 
gyria as above described, and those of other Ferns, with a view to assigning 
to it an approximate position in the system. 
In the bulky upright stock, with closely aggregated leaves and 
persistent leaf-bases, and showing at least in P . semicordata occasional 
dichotomy of the axis, characters are seen which are shared by such 
primitive types as the Osmundaceae ; this comparison is accentuated by the 
densely sclerotic tissues which compose it, and cover it externally. The 
deep involutions of surface which subtend the leaf-bases are closely similar 
to those seen in Anemia (compare Prantl, ‘ Schizaeaceen,’ PL III, Fig. 27, b), 
a comparison which is further supported by the similarity in structure of 
the leaf-trace. The enlarged base of the leaf reminds us again of that in 
the Osmundaceae, but the details of its structure do not correspond with 
any exactitude. The pneumatophores which it bears (which are present also 
in the upper leaf of the Eastern species) are striking objects, and might be 
expected to give a valuable basis for comparison; this is, however, in some 
degree discounted by the fact that they are not constant within the genus 
itself, being absent from the upper leaf in P. semicordata. But, putting 
this aside as not entirely depriving the comparison of value, the existence 
of similar organs in the Cyatheaceae is a matter for remark. Closely 
related causally with them, as already suggested above, are the very 
numerous glandular hairs which secrete mucilage; such hairs are found 
plentifully in the Osmundaceae of the present day, and in other relatively 
primitive Ferns, while somewhat similar hairs were characteristic also of 
the ancient Botryopterideae. The absence of flattened scales is a feature 
of importance for comparison ; it differentiates Plagiogyria from the 
Cyatheaceae, as well as from the genus Lomaria , and when taken together 
with other primitive characters which the genus shows, indicates a relation 
with the lower rather than with the higher forms of Ferns. 
