Fertilization in Collema . 
757 
species, that they are asexual conidia. Moller's results as to germination 
may or may not be correct, but the conditions in Collema pulposum certainly 
give a final and complete demonstration that the spermatia of the Lichens 
are male gametes and not asexual conidia. Even the author of such 
a tenuous hypothesis as that of the boring function of the trichogyne will 
hardly argue that these few cells buried deep in the thallus and never 
set free have their natural function as spores for the rapid asexual spread of 
the fungus. 
The conditions in the lichen here described throw new light on the old 
and much discussed question as to the relationship of the red Algae and the 
Ascomycetes. Harper (17), as have others before, has emphasized the fact 
that Pyronema , like the Laboulbeniaceae, forms an interesting link between 
the Lichens and the red Algae because of its conjugating tube. In those red 
Algae which have been investigated, the trichogyne is a tubular outgrowth 
from the egg-cell. In Pyronema this outgrowth is separated from the egg- 
cell by a wall. In the Lichens there are perhaps several cells between the 
receptive portion and the egg-cell. Collema pulposum is intermediate 
between those Lichens in which the trichogyne is composed of many small 
cells and Pyronema , where it is but one cell. But this species resembles 
Pyronema more than other Lichens, especially in the greater activity of the 
trichogyne and the manner in which it grows towards and coils about a sper- 
matium, and in the reduced number and greater fixity of the spermatia, 
thus making them more like antheridia. In attempting to homologize the 
spermatia of the Collemaceae and the antheridia of Pyronema, de Bary(ll), 
with his usual morphological acumen, pointed out that ‘If the spermatia of 
Physma remained fixed to their spermatiophores in order to conjugate with 
the archicarp, the only difference between the two forms would be one of 
conformation \ In the Collema I have described we have just such a form, 
and one still more useful for the homology because the spermatia are not 
borne in spermogonia and are so few in number. In the number and 
nature of its spermatia and the manner in which they are borne, this 
species of Collema forms about the most perfect conceivable connecting 
link between the aquatic red Algae with many non-motile male cells, which 
are, however, set free, and such terrestrial Ascomycetes as Pyroneina and 
the Mildews, where the male cells are reduced in number to one or two 
which remain permanently attached. 
The conditions as to sexual reproduction in Collema pulposum are 
also quite the same in principle as those in some of the Laboulbeniaceae, 
as fully described by Thaxter (32 and 33). In Zodiomyces one to three 
antherozoids bud from the tips of the antheridial appendages. From here 
the antherozoids fall and are then found lying loose about the bases of the 
perithecial stalks. The behaviour of the trichogyne is like that of Collema 
pulposum in that it grows towards where the spermatia are formed and there 
