386 Harper.—Sexual Reproduction in Pyronema 
are to fuse. The Lichen trichogyne is made up of many 
cells, while that of Pyronema is a single cell, but if two walls 
can be broken down to permit the passage of the male nuclei 
there is no reason why a larger number may not be. Under 
conditions which necessitate a longer trichogyne such as we 
find in the Lichens it is entirely natural that it should be 
a multicellular rather than a unicellular structure. 
Arranged according to the degree of complexity of the 
trichogyne we should have a series as follows: Batracho - 
spermum with the trichogyne a mere tubular outgrowth of the 
oogonium, Pyronema with this tubular outgrowth cut off by 
a septum so as to form a cell, Stigmatomyces with a second 
cell cut off as a trichophore at the base of the trichogyne, 
and Collema and other Lichens with the trichogyne divided 
by further septa into a row of cells, while the branched 
multicellular trichogynes of Teratomyces and Compsomyces 
afford examples of still greater complexity of development 
in this organ. 
Such a series of course cannot be regarded as showing the 
relationships of the different forms in the order indicated. 
It merely shows the possibility of such a series of forms 
having existed in the ancestry of the Lichen, and thus does 
away to a large degree with the difficulty which has been felt 
over the conception that such a multicellular hypha as the 
Lichen trichogyne could serve as a conjugating organ. 
Thaxter has made the very interesting observation that in 
some cases the trichogyne grows down at first toward the 
antheridium so as to seek out as it were the non-motile male 
cell and thus insure fertilization. In the genus Zoidiomyces 
the trichogyne grows down at first and receives the antherozoid 
on its tip when it turns and grows upward again into its 
apparently more normal position. This reversal of the ordinary 
relations of the sexes in the act of fertilization in which the 
egg-cell supplies an organ for seeking out the male cell is 
exactly what was observed to a less degree by Tulasne in 
Pyronema. The egg thus ceases to be a merely passive 
receptive cell when it has developed a trichogyne. And it 
