350 
F. Cavers. 
assume that all the other Anthocerotales have been derived from this 
type by more or less extensive reduction. 
Various writers have emphasized the characters which mark 
off the Anthocerotales from the remaining Hepaticae, and in 1897 
Gayet (8) proposed to raise the Anthocerotales to the rank of a 
class co-ordinate with the Hepaticae, restricting the latter term to 
the Marchantiales and Jungermanniales. The class was named 
Anthocerotes by Howe (14), who defined it in the formal systematic 
way, enumerating the peculiarities of the class as follows: “ (i.) a 
single large chloroplast to each cell, instead of several smaller 
chloroplasts as in the assimilative tissues of the Hepaticae proper; 
(ii.) the antheridia arise within the thallus—are endogenous in 
origin—and the walls of the immersed archegonia are confluent 
with the adjacent tissues ; (iii.) the presence of meristematic tissue 
in the capsule near its base, by the activity of which the capsule 
has a long continued growth, ripening spores towards its apex while 
forming new spore-mother-cells below ; (iv.) the presence, in pro¬ 
bably all cases, of a columella around which the archesporium is 
formed ; (v.) the presence, in many cases, of stomata on the capsule, 
with accompanying assimilative tissue. These five characters are 
peculiar to the Anthocerotes as distinguished from the Hepaticae 
proper, and they are characters of much significance. For ana¬ 
logies we must look chiefly in two directions—toward the Pterido- 
phyta and toward the Musci.” 
In the writer’s opinion, the significance of these characters of 
the Anthocerotales has been much exaggerated, and upon them has 
been based a certain amount of very doubtful speculation regarding 
the relationships of the Archegoniatae and the origin of the Pterido- 
phyta. From the summary presented here, it will be seen that 
very little importance can he attached to the first and second of the 
characters mentioned above. The number of chloroplasts per cell 
varies considerably. The “ endogenous ” origin of the antheridia is 
obviously a secondary character, derived from the normal exogenous 
type of antheridium development; the antheridia themselves agree 
closely with those of other Hepaticae, especially Sphaerocarpales, 
and though the development of the antheridial cavity is peculiar, it 
is easier to relate it to what is found in other Hepaticae than to 
establish analogies with the Pteridophyta. In the immersion of 
the archegonium in the thallus, the Anthocerotales do not in reality 
differ widely from other Hepaticae; the archegonium is partly 
embedded in Aneura , though in this case the neck is free. The 
