300 BOTANICAL GAZETTE [OCTOBER 
seem necessary to study the structure and behavior of the nuclei 
in the ascogonium quite closely before deciding that there is a 
fusion of nuclei in the ascogonium of any of the Pezizineae, and it 
is worthy of note that divisions have not been described in any of 
those mentioned above in which such a fusion is said to occur. 
This is particularly true of such an aberrant case as the occurrence 
of a second fusion following the sexual one in the life history of 
the same plant. 
ALTERNATION OF GENERATIONS 
When HorMe!ster used the term alternation of generations, 
he of course did not know of the alternation of the haploid and 
diploid number of chromosomes, but meant the alternation of two 
kinds of plants, one of which bore sexual and the other asexual 
reproductive bodies. Since the significance of nuclear phenomena 
has come to be better understood, many writers have been inclined 
to use the term alternation of generations as synonymous with the 
alternation of the haploid and diploid number of chromosomes, 
but the question may be asked as to whether the two things always 
necessarily coincide. If we take the cases of Alchemilla (MURBECK 
30), which has an embryo sac with the diploid number of chromo- 
somes, and Nephrodium (YAMANOUCHI 40), which produces sporo- 
phytes with the haploid number, there is of course no alternation 
of the haploid and diploid number of chromosomes, but from the 
standpoint of phylogeny there is an alternation of two kinds of 
plants. In Coleochaete, where the zygospore divides to form 4 
number of cells which produce zoospores, the cells formed from the 
zygospore may be regarded as an intercalated asexual phase, but 
reduction takes place at the first division of the zygospore (ALLEN 
1). Here there would seem to be, as FARMER has suggested, 2 
sporophyte which normally has the same number of chromosomes 
as the gametophyte. In the red alga Griffithsia bornetiana, LEwIs 
(25) thinks that the sexual plants and the mass of carpospores 
constitute an antithetic alternation of generations, while the sexual 
and tetrasporic plants represent the alternation of an homologous 
phase. According to this interpretation, the diploid number 0! 
chromosomes would extend through two distinct phases. 
