414 Cutting.— On the Sexuality and Development of 
is reported that the ascogonium is multicellular is in the archicarp of 
the Lichen type. A complete investigation of such a form has yet to 
be made, and these authors suggest that the ascogonium may really be 
unicellular before fertilization and develop into a multicellular structure 
afterwards as in Boudiera } Gymnoascus , and the Erysiphaceae. Whether 
this is really so further research alone can tell, but the facts so far recorded 
seem to be against this view. Baur (3) found that in Collema there were, 
from the beginning, a number of ascogonial cells, and he records the fact 
that after fertilization these cells divide, so that the number of ascogenous 
cells is thus increased. Darbishire (11) when working at Physcia pulveru- 
lenta paid especial attention to this point, and says that he does not find in 
this species the state of affairs which Baur stated for Collema ; the asco- 
gonial cells do not divide after fertilization. If, as Fraser and Chambers (16) 
suggest, the unfertilized ascogonium of the Lichen type is unicellular, it does 
not seem likely that the above-mentioned observers would have missed this 
point, especially as they were looking for divisions of the ascogonial cells. 
It has been pointed out that the ascogonium of such forms as Boudiera , 
Gymnoascus , and the Erysiphaceae develops into a multicellular structure 
after fertilization. This structure, although analogous to the ascogonium, 
which is multicellular before fertilization, can scarcely be regarded as 
its homologue. Such a multicellular structure would seem to have some 
advantages over the unicellular form, as in Humaria granutata and Lachnea 
stercorea , in that it allows of the origin of ascogenous hyphae over a larger 
surface. The ascogenous hyphae are therefore, at their origin, placed under 
conditions better suited for their nourishment than when they arise crowded 
together on a more limited area. The septate ‘ ascogonium ’ of the Erysi- 
phaceae might possibly be regarded as a structure adapted to the conditions 
best suited to the nourishing of the ascogenous hyphae. It will be remem- 
bered that in Gymnoascus (9) each of the cells of the septate £ ascogonium 5 
gives rise to ascogenous hyphae, while in what would seem to be the 
undoubtedly homologous structure in Erysiphe only one cell produces asco- 
genous hyphae ; in Phyllactinia , however, it would seem to be probable 
that more than one cell of the septate c ascogonium 5 produces branches, and 
it is possible that in the ancestral form of the Erysiphaceae all the cells 
branched. Further research on allied forms might throw some light on this 
point, which seems to me to present another argument in favour of the 
reduction of the Erysiphaceae. It is possible that a comparable series 
of reductions is present in the Ascobolaceae, but is here shown in a series 
of ascogonia septate before fertilization. 
Dangeard (10) records that in Ascophanus ochraceus he finds ascogonia 
like those of Pyronema , but without antheridia. On the strength of this he 
proposes to remove the genus Ascophanus from the Ascobolaceae. As the 
1 This plant may really be an Ascodesmis. 
