Ant hocerot ales. 
349 
stomata from the capsule-wall. Campbell (4, 5, 6, 7) has recently 
investigated a number of these species and has proposed the 
formation of a new genus, Megaceros, for their reception, the name 
being suggested by the large size of the sporogonium in most of 
these forms. This genus is further distinguished from Anthoceros 
by having green spores, a solitary antheridium, and as a rule several 
chloroplasts in the thallus-cells instead of a single large chloroplast. 
This new genus presents interesting points of contact with the other 
three genera of Anthocerotales. It resembles Anthoceros in the 
form of the thallus and its apical growth, and in the form and size 
of the sporogonium ; Notothylas in the large amount of sporogenous 
tissue developed in the apical region of the sporogonium, above the 
columella; and Dendroceros in the characters already mentioned 
above, also in the green spores and the early development of the 
embryo. 
The facts at present known concerning the morphology of the 
Anthocerotales appear to the writer to suggest that (i.) the forms 
constituting Campbell’s genus Megaceros are at least as sharply 
separated from the other species of the old genus Anthoceros as 
are those comprised in the genus Notothylas ; (ii.) the species of 
Dendroceros form a still more natural group; (iii.) it is an open 
question whether Notothylas is a reduced form. The organisation 
of the Notothylas sporogonium need not necessarily be interpreted 
as due to reduction from the Anthoceros type; the reverse inter¬ 
pretation does not appear to be excluded by the fact that both the 
endothecial and the inner amphithecial tissues produce spores. 
Apart from the close agreement of its gametophyte with that of 
Anthoceros, we find in the Notothylas sporophyte a series of forms 
showing varying and unfixed sterilisation of the central tissue, with 
progressive shifting of spore-production to the inner layer of the 
wall-tissue. Assuming the absence of reduction in the Notothylas 
types, we might regard Anthoceros Hallii as forming a link between 
the more primitive forms of Notothylas and the species of 
Anthoceros with stomata and well-developed assimilating tissue, while 
Megaceros and Dendroceros have arisen independently from the 
primitive forms of Notothylas, in which the sterile cells of the arche- 
sporium are short and isolated, the assimilating tissue of the sporo¬ 
gonium is feebly developed, and stomata are not formed. If we 
regard the typical Anthoceros capsule, with its stomata and its 
efficient assimilating arrangements, as being primitive, we must 
