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Freda M. Baehmann 
strongly suggests that a fusion is occurring or about to occur. The variable 
number of nuclei in the cells of the ascogenous hypliae, and the fact that 
each nucleus divides entirely independently of every other nucleus in 
the cell, seem to me to be evidence against a pairing of the nuclei of these 
cells, although it is true that some of the cells are binucleate. But whether 
there is a single or double fusion of nuclei in C. pulposum there can be 
no doubt as to the difference between the chromosome numbers in the 
first and third divisions in the ascus, and in this respect my results agree 
with those of Fraser, Maire, and Fraser and Brooks. It is generally 
agreed that synapsis is a stage in the prophase of the heterotypic division. 
This stage is well marked in the form I have studied. The number of 
cliromosomes appearing in the first division is about twelve. This should 
be the reduced number, to agree with the conditions in the higher plants, 
in which the reduced chromosome number always appears in the hetero- 
typic division. But in the third division in the ascus only half as many 
namely, six, cliromosomes appear. It seems certain then, that there is 
a second reduction in Collema pulposum, probably in the second division 
in the ascus. In the ascomycetes which Harper studied, he found the 
same apparent number of chromosomes throughout the life history. 
To explain the three divisions in the ascus he says (52, p. 82): “The most 
natural assumption would seem to be that the chromosomes are quadri- 
valent in the nucleus of the ascus rather than bivalent, as in ordinary 
spore mother cells, and that. in two of the divisions in the ascus chromo- 
somes are separated instead of in one division, as in the ordinary case.” 
But in C. pulposum and those other ascomycetes in which the number 
of chromosomes in the third division is only half of the number on the 
spindle of the first division, we have even better evidence than in Phyllac- 
tinia of the Separation of whole chromosomes in two successive divisions. 
Such evidence is certainly a strong argument in favor of two nuclear 
fusions. 
The nature of fertilization in lichens. 
Just in what fertilization consists in the lichens will probably re- 
main an unsettled problem until many workers have attacked it in various 
members of the group. Baur (3) has suggested that a number of ascogone 
cells may be egg cells; this would necessitate the migration of a number 
of male nuclei through the trichogyne or eise a repeated division of the 
spermatium nucleus to form a number of functional male nuclei. But 
he thinks both these things improbable, since the trichogyne fuses with 
but one spermatium, and on the other hand, such a division of the male 
