382 Bower r — Studies in the Phytogeny of the Filicales . 
is virtually absent both in the mature and in early developmental stages 
(e.g. B. lanceolatum ), a state which compares with Matteuccia or Plagiogyria\ 
to those in which it is present, and even developed to a considerable size, as 
in B. spicant or B. gibbum. There is an underlying uniformity in the form 
and anatomical structure of the whole plant, notwithstanding fluctuations of 
detail, and a similarity in the scales and glandular hairs, which indicate that 
the series is a natural one of real affinity. This, indeed, has never been 
a matter of serious question. 
Examples will next be taken of Eu-Blechnum , which is characterized 
by the more or less complete absence of dimorphism. Here it may be 
difficult, or even impossible, to tell the sterile from the fertile leaves until 
they are examined from below. The sori then appear as linear structures 
parallel to the midrib, and lying as a rule close to it on either side. This 
state has been seen to occur abnormally in B. gibbum and B. capense , and 
it thus appears that the two sub-genera are closely allied, while we shall 
anticipate that the development of the fertile pinnae will differ rather in 
detail than in principle. The facts show that the anticipation is justified. 
(I) Blechnum ( Eu-Blechnum ) brasiliense y Desv. 
This is a large, erect, subdendroid species, with the bud covered by 
dark scales, which remain permanently on the axis and leaf-bases. In 
addition to these, the mucilaginous glandular hairs described in detail by 
Gardiner and Ito (Ann. of Bot., vol. i, p. 27) are present, a type that is 
prevalent in the genus. The leaves are all alike in outline and their pinnae 
relatively broad. It will be unnecessary here to describe more than the 
origin of the sorus and of the largely developed flange. The wing of the 
fertile pinna arises in the same way as that of the sterile, that is by the usual 
marginal segmentation (PI. XXV, Fig. 12, <2), and the sorus does not make 
its appearance until the wing has attained considerable size. It originates 
as a rather massive upgrowth at some distance from the marginal segmenta- 
tion, which has here no direct part in its formation (Fig. 12, b, c). The 
upgrowth soon shows a greater activity on the side remote from the midrib, 
so that it becomes tilted over, facing centrally (Fig. 12, d). Very soon the 
‘ indusium ’ appears, overarching the receptacle which bears the sporangia. 
It grows rapidly (Fig. 12, e) s taking a strongly curved form, and its apex 
coming in close relation to the projecting midrib ; the result is a very perfect 
protection of the receptacle. Upon this the sporangia arise, with the usual 
segmentation. Their order of succession in the sorus at first shows clear 
signs of a gradate sequence (Fig. 12, d , e) y but this is not maintained, and 
in later stages the sorus becomes pronouncedly of the mixed type. The 
progression from the more primitive to the derivative state is here, as in 
some other cases in Ferns, reflected in the individual development. Beneath 
the sorus is the usual vascular commissure, which is indicated in Fig. 12, e, 
