DEVELOPMENT OF PYRONEMA CONFLUENS VAR. INIGNEUM 295 
Cubbin ('lo) for Helvella and by Brown ('lo, 'ii) for Leotia, Lachnea 
and Geoglossum. 
When a penultimate cell gives rise to an ascus, the two nuclei 
fuse, after which the fusion nucleus goes into synapsis. After synapsis 
a spireme emerges which contracts and divides into five chromosomes. 
These become arranged on the spindle and five daughter chromo- 
somes pass to each pole. In doing so, they do not divide as in Lachnea 
(Brown, 'ii), but usually become dumb-bell shaped. In the next two 
divisions giving rise to eight spore nuclei, and in the first division of the 
spore nucleus, there are also five chromosomes. It thus appears that 
the same number of chromosomes, five, persists through all the 
divisions of the life history of the plant. 
Discussion 
The fusion of the antheridium and trichogyne of Pyronema con- 
fluens was described by the Tulasne Brothers in 1866. Their descrip- 
tion was confirmed by Kihlmann ('83), who regarded the fusion as a 
proof of the sexuality of this form. 
Van Tieghem ('84), grew Pyronema under various conditions, and 
described the course of development as being markedly influenced by 
the different treatments. According to this writer, under certain 
conditions, the chief of which is the presence of sufficient moisture, the 
ascogonia and antheridia are large and the trichogynes fuse with the 
antheridia. Under other conditions, particularly a certain amount 
of dryness, the antheridia and ascogonia are smaller. Under still 
other conditions, when the dryness passes a certain limit or the tem- 
perature falls below a certain point, the cells which usually develop 
into ascogonia and antheridia are smaller and more numerous than 
in the other two cases and there is no differentiation into ascogonia 
and antheridia. Since development continued in all of these cases, 
Van Tieghem regarded the last as an argument against the sexuality 
of Pyronema but said that De Bary would regard it as a case of 
apogamy. Harper ('00) found that, after the fusion of the antheridium 
and trichogyne of Pyronema, the nuclei of the antheridium migrated 
into the trichogyne and then into the ascogonium. According to 
Harper this was followed by a fusion in pairs of the nuclei in the asco- 
gonium. Dangeard ('05) described the fusion of the antheridium and 
trichogyne but said that the nuclei of the antheridium did not migrate 
into the ascogonium. Claussen ('07) confirmed Harper's account of 
