MARCHANTIALES 263 
affinity with the Marchantiaceae, though showing a similar relation of 
spore-mother-cells and elaters. Since the whole mass is uniform in origin, 
and since the similar mass in Avccéa is wholly fertile, it is the natural 
conclusion that certain of the potentially fertile cells have been sterilised 
to form the elaters: or, in other words, remain as somatic cells without 
undergoing chromosome-reduction. The final function of the elaters is to 
assist mechanically in the dispersal of the mature spores; but it is possible 
that in such a plant as Fegatella (Conocephalus) they may in some 
degree assist in the early nutrition of 
the cells which remain fertile. This 
seems almost certainly to be the case 
in Corsinta, and also in those genera 
of more doubtful affinity, viz. Sphaero- 
carpus, Geothallus, and Rzella, where 
the sterile cells are not mechanically 
strengthened by spiral or annular 
thickenings of their walls: they are 
here recognised as ‘nutritive cells,” 
and they undoubtedly aid in the supply 
of nourishment, and perhaps also in 
dispersal of the spores by swelling 
of their mucilaginous remains. The 
obvious importance of these nutritive 
cells, as well as of the elaters, is 
further evidence of the probability that 
a progressive sterilisation, or conversion 
of reproductive into somatic cells, has 
occurred. 
In the Marchantiaceae there is Fic. 123. 
regularly present at the distal end of Cyathodium cavernarum, longitudinal section 
F of an almost mature sporogonium showing apical 
the capsule a small mass of tissue disc. 200. Above, the apical disc of the same 
within the one-layered wall, which lade pete Rese Pe as 
remains sterile, and comes away at 
dehiscence as a cap, or lid. This also originates from the archesporium : 
its development has been clearly shown by Lang in Cyathodium: Fig. 123 
illustrates the apex of a sporogonium, and from comparison of the young 
state it is plain that certain cells of the archesporium are told off as 
sterile from the first. 
From these notes it appears that in the Marchantiaceae, as compared 
with the Ricciaceae, the evidence is strong for the conclusion that the 
sporogenous tissue is liable to be reduced at various points by diverting 
cells, or groups of cells, from their original function as fertile cells: the 
somatic functions which they then perform have obvious uses, and this 
gives biological probability to the conclusion. 
