388 Bower. — Studies in the Phytogeny of the Filicales. 
leaf-gap, just before it opens, a root-trace passes off. Closely above it, from 
right and left of the gap, the two equal foliar traces spring. These pass 
obliquely outwards without further subdivision into the petiole. Tangential 
sections show how regular is the disposition of these (Text-fig. 7, b). The 
root-trace may at times be slightly diverted to right or left, but it commonly 
lies immediately below the leaf-trace. The whole scheme is one of the 
most regular observed in Blechnum , but the leaf-trace is simpler than is 
frequently the case in the larger species. It corresponds rather to that of 
Matteuccia. It is possible that its simplicity may be correlated with 
xerophytic reduction, which has undoubtedly played its part in the moulding 
of the species. 
The sporophylls are upright, very narrow, and commonly unbranched. 
Text-fig. 8 shows the outline of the transverse section, with its two vascular 
strands in the midrib. The margins are strongly rolled downwards, and 
the indusial flap fits closely into the curves of the enlarged midrib, giving 
very perfect protection to the sori. Superficially there are deep watery 
cells, shown diagrammatically in the 
drawing, which contracting at maturity 
unroll the lateral flaps, and allow freedom 
to the spores. 
From early stages it is seen that 
there is as usual a row of marginal initials, 
with alternate segmentation (PI. XXVI, 
Fig. 14, a). A considerable wing is 
thus formed on either side. Upon the 
abaxial surface of this, and at a dis- 
tinctly intramarginal point, an upgrowth arises (Fig. 14, b, c). From 
this the indusial flap springs, while the receptacle lies between it and 
the midrib (Fig. 14, d). But the form of the receptacle is here not convex 
when mature, but may be distinctly concave (Fig. 14, d , e ) ; moreover, it 
may clearly be seen that the sporangia of different ages are intermixed. 
These features are here more marked than in any of the preceding species ; 
they suggest that B . Patersoni is derivative and advanced as compared 
with them. Further, it is seen that the area of the sorus is not sharply 
restricted, but spread over a considerable space between the midrib and the 
indusial flap, a point which will be important for comparison with the species 
to be subsequently described. 
Mettenius figures for B. Patersoni a specially large type of sporangium 
with long and thick stalk, and a head with a continuous oblique annulus ; 
and he states that such sporangia are found seated on the most projecting 
point of the receptacle (Fil. Hort. Lips., p. 61, PI. IV, Fig. 7). In face of 
his circumstantial statement and of the drawing which he gives, I do not 
express any doubt of these interesting and comparatively important facts ; 
Text-fig. 8. Transverse section of a 
pinna of Blechnum Patersoni (R. Br.), 
Mett. Semidiagrammatic. x 24. 
