JUNGERMANNIALES 267 
clue to the steps of evolution of the elaterophore: that it arose by partial 
sterilisation of the archesporium, with the consequence that the fertile 
zone is relegated to the exterior. The development in Féé/ia is essentially 
the same, but the attachment of the elaterophore is to the base of the 
capsular cavity. It is worthy of note that these modifications occur in 
the Anakrogynous Jungermanniaceae, which, as we have already seen, are 
more advanced than the Akrogynous as regards the differentiation of the 
seta and capsule. 
Fi. 129. 
ry A, median section of young sporogonium ot Axeura ambrosioides. The internal mass 
of cells of the sporogonial head (‘‘archesporium”) is already differentiated so as to 
indicate the sterile elaterophore, and the outer fertile region. B, the same, older: the 
indications of sterilisation have extended outwards, and it is only the peripheral fringe of 
cells (shaded) which will be sporogenous. C, transverse section of the same. 150. 
It thus appears that in the Jungermanniales partial sterilisation of the 
sporogenous tissue has occurred analogous to that in the Marchantiales ; 
but in addition there is reason to believe that the elongated seta has 
here originated also by relegation of the spore-producing function from 
the lower segments to the upper, or even to that tier of them which is 
apical. ‘ 
C. THE ANTHOCEROTALES. 
The Anthocerotales stand clearly apart in the mature characters of the 
sporogonium. Its large size and early freedom from the calyptra, the 
continued intercalary growth, and the specialisation for self-nourishment 
are external characters which dissociate the family from other Liverworts : 
while internally, the presence of a columella, at least in the larger forms, 
and the origin of the archesporium from the outer cells of the young 
capsule, also point in the same direction. There are, however, differences 
of detail within the family, which indicate with some degree of probability 
a line of derivation from a Jungermanniaceous type, the nearest approach 
being in the ‘genus JVo/othylas. 
