32 Bower . — Studies in the Phytogeny of the Fi lie ales. VI. 
of more mature states, referring to Mettenius, 1 and giving a series of 
diagrammatic drawings illustrating the spread of the sorus over the leaf- 
surface. The origin of this Acrostichoid type is clearly from Blechnum : 
the habit, anatomy, and corresponding glandular hairs, as well as the soral 
characters and form of the spores, show this. A phyletic series based on 
such characters was shown by me to lead from a type like Matteuccia inter- 
media. with separate sori, to Blechnum with sori fused above a vascular com- 
missure, and then on to the Acrostichoid state as seen in Stenochlaena. 
Another example of a similar progression is seen in Brainea , but this has 
probably been along a distinct line from Stenochlaena. Brainea is in fact a 
small tree-Blechnoid, in which after abortion of the indusium (phyletic 
margin of the leaf) the sorus had spread outwards over the leaf-surface. The 
genus Hymenolepis is still very uncertain in character and affinities, but 
probably it also is of Blechnoid origin, related through Dicranoglossum and 
Taenitis. The conclusion is then that among the Blechnoid Ferns a 
passage to an Acrostichoid state has probably occurred along more than one 
phyletic line. 
Another isolated case, which has been regarded as related to the 
Gymnogramminae and Cheilanthinae, is the genus Trismeria (perhaps also 
Microstaphyla , Presl.). With vascular anatomy, which indicates a similar 
grade to that of Llavea or Plagiogyria , it shows an Acrostichoid condition 
of the sorus. This might readily have been produced from the state seen in 
the plants named, by spread of the sorus on to the leaf-surface intervening 
between the veins. 
The genera Polybotrya and Stenosemia are placed by Diels with 
his Aspidiinae. Frau Schumann ( 1 . c., pp. 252-8) concludes that these 
genera are akin to one another, and gives interesting figures illustrating 
successive steps of spread of the sporangia over the extended surface of the 
sporophyll. Though these do not demonstrate the affinity of these Ferns, 
still the habit of the sterile leaf, as well as the vascular anatomy, indicates an 
Aspidioid relation. The latter has been examined in P. osmundacea, H. B. 
Willd., which has its axis greatly elongated, with long internodes, in accor- 
dance with the climbing habit. About six meristeles are arranged in a ring 
in the transverse section. The leaf-gaps are drawn out to great length. 
The leaf-traces enter the axis as numerous separate strands, and pursue 
a course downwards for a distance of several internodes through the cortex, 
thus giving the appearance of a cortical series. Ultimately they insert 
themselves on the sides or base of the leaf-gaps. P. cei'vina (L.), Klf., shows 
similar characters, but only three meristeles appear in the transverse 
section. The leaf-traces behave in the same way as in P. osmundacea , but, 
the axis being much less elongated, the appearance more nearly resembles 
that of N ephrodium. In fact, the vascular system is a dictyostele with sub- 
1 Fil. Hort. Lips., p. 61. 
