F. Cavers. 
38 
Jungermannian and Anthocerotean characters, and since the 
Anthocerotales diverge considerably from the other Liverworts, 
at any rate in the development and structure of the sporogonium, 
we might assume that the hypothetical primitive “ Sphaero-riccia ” 
type gave rise on one hand to the Sphaerocarpales, Marchantiales, 
and Jungermanniales, and on the other to the Anthocerotales and 
Sphagnales. It must be admitted, however, that the gap between 
the Sphagnales and the Anthocerotales is much wider than that 
between the Anthocerotales and the other Liverworts. The four 
groups of lower Bryophytes (Sphaerocarpales, Marchantiales 
Jungermanniales, Anthocerotales) agree with each other, and differ 
from the higher Bryophytes, in the development of the sexual 
organs hy means of intercalary growth and not by an apical cell, 
in having unicellular rhizoids, in the absence of an apical cell from 
the leaves in the case of foliose forms, and in the presence (except 
in Ricciaceae) of sterile cells (typically developed as elaters) in 
the archesporium. 
In the Bryales, the most striking advance upon the lower 
groups is the evolution of the peristome. If we assume that some 
at least of the cleistocarpous Bryales are primitive, it would be 
easy to trace from types like Archidium and Phascum a series of 
lines leading up to the typical Bryales, and this possibility should 
not be lost sight of. There has been a general tendency to regard 
these cleistocarpous genera as reduced, but in the writer’s opinion 
the question of their position and affinities is quite as open as in 
the case of the Ricciacese. However, setting aside these doubtful 
forms, the genus Andrecea appears to point to a possible connecting- 
link between Sphagnales and Bryales, and also to throw some light 
upon the origin of the peristome. In Andrecea , the archesporium, 
though arising in the outermost zone of the endothecium, is 
completed above—just as in Sphagnum and Anthocerotales—by a 
zone of tissue extending across the entire endothecium, so that the 
columella is incomplete and is covered above by the dome-like 
archesporium. 
In the writer’s view, there appears to be a definite correlation 
between the form of the archesporium and the fate of the apical 
tissue of the capsule. When the archesporium is dome-shaped, 
the sterile apical tissue is practically cut off from the stream of 
food materials brought upwards from the gametophyte, through the 
conducting-strand of the seta and thence through the columella of 
the capsule, and these materials are almost entirely used up in the 
