414 Bower*— Studies in the Phytogeny of the Fiiiccdes . 
the single sori was again on the same plan. Where the sori were of the 
Diplazium type, this results merely from the duplication of the soral 
characters back to back upon the same vein, or, where the branching of 
the vein has begun, upon the vein in various degrees of division. The real 
nature of these duplicated sori has been explained above (p. 412), and their 
structure accords with the views already expressed. 
Finally, though the anatomical facts are not very distinctive, they may 
be stated here. The axis of various species examined contains a dictyostele 
with leaf-gaps, from the sides of which the two broad straps of the leaf-trace 
spring. The root-traces arise from the outer limit of the meristeles at points 
below the openings of the leaf-gaps. Thus the system is of the same type 
a. 
Text-fig. 19. a , transverse section of the stock of Asplenium obtusatum, Forst. The leaf- 
trace resembles that of Matteuccia. x 3. b, a similar section of Asplenium alalum , H. B., 
which shows the fusion of the strands in the petiole, x 12. 
as that of Blechnum (Text-fig. 19, a). Passing into the petiole, the two strap- 
shaped vascular strands may remain separate, as they do in the large 
A. marginatum (Text-fig. 19, a), or, especially in smaller species, they may 
coalesce upwards to form those peculiar X-shaped vascular tracts so fully 
described by Luerssen (Rab. Krypt. -Flora-, iii, pp. 149, &c.). This is seen 
in A. alatum (Text-fig. 19, b). In this they show a close similarity to 
what is seen in Scolopendrium. These features strengthen the relation 
of Scolopendrium to Asplenium , which has never been questioned. And 
further, the varieties of Blechnum punctulaium link both of these without 
any doubt to the genus Blechnum as ultimate derivatives from that 
type of P"erns, 
