Phytogeny of Marchantiales. 175 
female receptacle should have made more rapid advance in elabora¬ 
tion than has been the case with the male receptacle. The function 
of the antheridia is accomplished when they have matured and 
liberated the antherozoids; but the archegonia and the tissues 
surrounding them are concerned with the important and often 
prolonged processes of nourishing and protecting the developing 
sporogonia. Moreover, the working out of efficient methods for 
spore-dispersal has clearly played an important part in the evolution 
of the carpocephalum, and the first decided step in this direction 
would be the elevation of the sporogonia above the general surface 
of the thallus. 
The starting point in the evolution of the carpocephalum is 
evidently to be found in the Corsiniaceae, which are not very far 
removed from the Ricciaceae. No known species of Riccia shows a 
definite archegonial group, but in Tessellina we get an approach to 
a female receptacle, for the archegonia are no longer sunk in the 
general thallus tissue. The envelope which grows up around each 
archegonium may be compared with the involucre of higher forms, 
and if the archegonia were developed in small groups and each 
group were raised above the thallus on a stalk formed by growth of 
the underlying tissue, we should have a carpocephalum comparable 
with that of Clevea or Plagiochasma. In the latter genera, however, 
the archegonia are not developed until the receptacle has arisen as 
an outgrowth behind the growing-point of the thallus, and they are 
developed upon this outgrowth, each archegonium becoming sur¬ 
rounded by an involucre. The gap between Tessellina on one hand 
and Clevea and Plagiochasma on the other is to a large extent 
bridged by Corsinia, where an outgrowth arises in the midst of the 
archegonial group in a depression of the thallus, the outgrowth 
appearing after the archegonia have begun to develop. In Corsinia, 
therefore, we have a primitive carpocephalum which arises at a late 
stage as compared with the carpocephalum of Clevea or Plagio¬ 
chasma ; its further development depends upon the fertilisation of 
the archegonia, and in any case it never becomes more than a scale 
which is thrust to one side during the development of the sporo- 
gonium, the latter being protected from the first by its own thick 
calyptra rather than by the incipient carpocephalum. 
The affinities of the Targioniaceae and of Monoclea have already 
been discussed, and we have seen that the involucre of these forms 
may be directly compared with the hood-like scale which arises 
behind the archegonial group of Boschia. Cyathodium has clearly 
