384 Harper*—Sexual Reproduction in Pyronema 
tance. With its one-celled trichogyne Pyronema forms an 
interesting link between the Florideae, where the trichogyne 
is a mere beak on the oogonium, and the Lichens, where it is 
a row of cells. 
In the discussion of the question as to whether the tendency 
to dioecism is a sufficient explanation for the appearance of 
spermatia in the place of attached antheridial cells, there is 
little evidence to be added to that presented by De Bary. 
As to the general similarity of the apothecium of Pyronema 
and the cystocarp or favella of the red Algae there can be 
no question. In each we have a fertilized cell which by 
vegetative growth develops a mass of spores, in the one case 
ascospores, in the other carpospores. That in the one case 
the spores are produced by free cell-formation, while in the 
other they are budded off from the surface of a placental 
cell or cells does not affect the resemblance so far as its 
general features are concerned. Whether the vegetative 
growth of the fertilized cell is to be interpreted as an alterna¬ 
tion of generations in either or both cases remains to be 
settled by a more accurate account of the chromosome-number 
in the two stages. That there is no oosphere rounded up and 
set free in an oogonium in either case cannot be regarded 
as a fact of very fundamental significance. The fertilized 
egg of the Moss or Liverwort remains in parasitic relationship 
with the mother plant through its whole development. In 
Sphaerotheca, for example, we need only consider that the 
parasitic relationship is more perfect, so that the egg is never 
set free from actual vegetative union with the parent plant. 
However the nature of the growth directly from the egg may 
be interpreted, there is no question that the protective hyphal 
envelopes developed around the ascogonium and asci are 
nothing but a further outgrowth of the sexual mycelium 
comparable to the development of the archegonium and 
calyptra in the Moss. 
After what has been said of the relationship of Pyronema 
and the red Algae it will be seen at once that the connexion 
of the former with the Laboulbeniaceae must be both inter- 
