231 
Inter-Relationships of the Anacrogynce. 
be readily derived, by the differentiation of the thallus into a 
cylindrical midrib and single-layered wings. This Symphyogyna 
plexus has evidently given rise to Dlyttia, Podoinitrium, Umbraculum, 
and Metzgeria. Of these four genera, Blyttia differs from Symphyo- 
gyna in little except the development of a tubular perianth, but in 
the other three the sexual organs are restricted to ventral branches. 
Metzgeria shows the simplest type of sexual branches, but the most 
highly developed elaterophore ; its midrib is slender and lacks the 
conducting strand present in the other genera of the plexus, and 
neither perianth nor involucre are developed. Umbraculum may be 
derived from a Symphyogyna- like form by the relegation of the 
sexual organs and the development of a perianth after fertilisation. 
In Blyttia and Podoinitrium, which have many points of resemblance, 
the perianth is developed before fertilisation, and outside it there is 
a cup-like involucre; probably Podoinitrium bears somewhat the 
same relation to Blyttia that Umbraculum does to Symphyogyna. 
A cup-like involucre and a perianth are also present in Morchia, 
which further resembles Blyttia, Podoinitrium, Umbraculum, and 
Symphyogyna, in having conducting strands, though these are feebly 
developed. But Morchia does not appear to be closely related to 
the Symphyogyna series, and the same double investment of the 
sporogonium is found in Calycularia, which apparently belongs to 
the Pellia line. It is clear that the Aneura line is peculiarly rich 
in parallel developments, exhibited by the evolution of “ Dendroid ” 
thallus habit, of conducting strands, of leaves, of specialised sexual 
branches, and of sporogonial investments (involucre and perianth). 
In the Pellia line, we may distinguish two diverging branches. 
One of these leads through Pellia and Calycularia to the foliose 
genera Blasia and Cavictilaria. The other leads through Pellia to 
Noteroclada and the other typical foliose Codoniaceae, and probably 
also to the Calobryaceae and the Acrogynae. Treubia is an isolated 
genus, with its peculiar vegetative structure and the investment of 
the sporogonium by a massive calyptra instead of a perianth. 
Fossombronia is closely allied to Noteroclada, but its sporogonium is 
very like that of Petalophyllum, though the vegetative organisation 
of the latter is peculiar. The Calobryaceae make a distinct approach 
to the Acrogynae, but they appear to form a blindly ending line of 
development, and it is more probable that the Acrogynae have 
arisen from a type like Noteroclada. 
