424 Bower.—Studies in the Phytogeny of the Filicales. 
of the Helicogyratae. The stock of these Ferns was not examined, but, on 
other general grounds, he referred them to the genus Lomaria , not seeing 
in the peculiarity of their sporangia any sufficient reason for removing them 
from that genus. A more full description with careful drawings was given by 
him in the following year, 1 but again without the axis having been observed. 
In leaving these species within the genus Lomaria , notwithstanding the 
divergence of structure of their sporangia, Kunze remarks ( 1 . c., p. 62) that 
in his view the microscopical features will never lead to a natural arrange¬ 
ment, and they can only be used as indications ; the species may, however, 
be designated as a section of the genus under the name of Plagiogyria. 
Next in point of date came the monograph of Mettenius, 2 in which he 
separated the sub-genus from Lomaria under the generic name of Plagiogyria ; 
but Sir William Hooker 3 still retained it as Lomaria , where it remained in 
the c Synopsis Fi-licum \ 4 His reasons for this are explicitly stated ( { Species 
Filicum ’, iii, p. 2); the passage is interesting as illustrating the attitude of 
a great systematist in the year i860; he wrote: ‘I am not disposed to 
retain Plagiogyria separate from Lomaria , although constituted by a botanist 
by no means addicted to establishing new genera on slight grounds. It 
has peculiarities in the base of the stipes and in the presence of certain 
glands called by Mettenius aerophorae ; but notwithstanding this structure, 
and even should the capsules in all the species referred to Plagiogyria prove 
to be helicogyrate, yet the habit and sori are so entirely in accordance with 
true Lomaria that, unless the student has the opportunity of examining 
very perfect specimens, or unless he examines the structure of the annulus 
of the very minute capsules under the high power of a microscope, the 
genus cannot be identified. Kunze, who first recognized the physiological 
differences, only proposed to form a group or section, under the name of 
Plagiogyria , but even that would be inconvenient to retain in a work whose 
main object is to assist the tyro in the verification of genera or species ; 
and natural habit is often a safer guide than minute microscopic characters.’ 
On this footing convenience of use for purposes of recognition takes 
precedence over natural affinity in the systematic method. 
The monograph of Mettenius above alluded to established Plagiogyria 
as a substantive genus, notwithstanding the divergent opinions of Hooker 
and of Kunze. Comparisons had been drawn by various writers between 
the Ferns of the Plagiogyria section of Lomaria , and other species of 
Lomaria , and of Stenochlaena on grounds of external form; but it was 
pointed out by Mettenius that there were broad differences notwithstanding 
the superficial similarity ; the characters recognized by him as distinguishing 
1 Kunze, G.: Farrnkrauter (Schkuhr’s Farrnkrauter, Supplement). Zvveiter Band, p. 61, 
Taf. CXXV, and 91, Taf. CXXXVIII. 
2 Ueber einige Farrngattungen. II. Plagiogyria , 1858. 
3 Species Filicum, iii, p. 2, i860. 4 1. c., p. 182, 2nd ed., 18S3. 
