44 
F. Cavers. 
the archesporium—being derived from the endothecium. On the 
other hand, however, Anthocerotales and Sphagnales are separated 
by differences in the development of the sexual organs, and it would 
appear that these differences are absolutely characteristic of the 
two generally recognised divisions of Bryophyta. In all Hepaticae 
that have been investigated, both the antheridium and the arche- 
gonium show intercalary growth, while in all Musci the young sexual 
organs grow by means of an apical cell. This generalisation has 
been challenged by Gayet, who claims that in all the groups of 
Bryophyta, excepting Anthocerotales, an active apical cell is present 
which produces the neck-cells but not the canal-cells, the latter 
being formed from the same mother-cell as that which gives rise to 
the oosphere and ventral canal-cell. According to Gayet, Autho- 
ceros is the only Bryophyte in which the entire growth of the arche- 
gonium is intercalary. Campbell has pointed out that Gayet’s 
methods are quite inadequate for the purpose of deciding this 
somewhat difficult question, and the results of the comparatively 
few recent researches in which the development of the archegonium 
has been carefully followed have shown that in Hepaticae (including 
Anthocerotales) the archegonium does not at any stage grow by 
means of an apical cell, while in Mosses (including Sphagnum ) an 
apical cell is present, its segments giving rise to the entire neck and 
its canal-cells. 
In the writer’s opinion, if any departure at all is to be made 
from the customary classification of the Bryophyta into Hepaticae 
and Musci, it would be better to divide the whole phylum into the 
ten independent groups enumerated above, without setting the 
Anthocerotales and the Sphagnales apart from the remaining 
Hepaticas on one hand and the remaining Musci on the other. 
LITERATURE OF TETRAPHIDALES, POLYTRICHALES, 
BUXBAUMIALES, AND EU-BRYALES. 
(From the extensive literature on the higher Mosses, I have selected for 
citation here only the more important works dealing with the morphology of 
the groups mentioned ; works relating to the vegetative organs and to the 
systematic and floristic study of Mosses are omitted, except in cases where 
they have a direct bearing upon the phylogeny of the Bryophyta in general and 
of the Mosses in particular). 
1. Bastit, E. “ Recherches anatomiques et physiologiques sur la tige et la 
feuille des Mousses.” Rev. gen. de Botanique, 1891, 
116 pp. 
