CHAPTER XXII. 
II. MUSCI. 
THE Mosses for the most part show greater uniformity of plan in their 
sporogonia, and give less indication of the steps of their evolution than 
do the Liverworts. It is a question open for discussion what, if any, 
are the genetic relations of these two classes. Whatever view may be 
held on this point, there are certainly strong features of similarity between 
their sporogonia. Without necessarily accepting these resemblances as 
indications of near genetic affinity, they must at least be held to point 
a strong analogy between the two series: so strong indeed that it will 
go far to justify an application of a theory of sterilisation in the Musci, 
even where the gradual steps of the process are less clearly indicated 
than they are in the Liverworts.. 
The Musci include the Sphagnales, the Andreaeales, and the Bryales: 
these are sufficiently distinct in their sporophyte-structure to require 
separate description; andethe Sphagnales will be taken first, as showing 
the clearest analogies with the Hepatics. 
A. SPHAGNALES. 
Notwithstanding the strong divergence of their gametophytes, both in 
form and in structure, the sporogonia of the Sphagnales and Anthocerotales 
show marked similarity, both in form and in development. Alone among 
the Mosses the embryo of Sphagnum segments by successive transverse 
walls, like a Liverwort: there is no continued apical growth, the further 
enlargement after the first segmentations being intercalary in the segments 
already laid down (Fig. 132 a): of these only the upper three or four 
go to form the capsule: the rest form the short seta, and the foot. In 
the upper region each segment divides into quarters, which again divide 
so as to form in each transverse section a central group of four (endothecium), 
and a peripheral series (amphithecium) (Fig. 132 c, D, E). The former 
give rise to the columella alone, which is in Sphagnum a bulky mass 
