469 
Cytology of the Ascomycetes . 
Irregularly shaped and multinucleate spores, and also asci which 
contained more than two. nuclei at their formation, were several times 
observed. 
The paraphyses are septate ; in the earlier stages of development their 
nuclei are small and contain a single nucleolus, the rest of the stainable 
material being regularly distributed (Fig. 46). Later the nuclei become 
enlarged and vacuolate, and the nuclear contents are massed into deeply 
staining lumps (Fig. 47). 
The Divisions in the Ascus. 
The chromosomes have been counted in comparatively few Ascomycetes, 
a great part of our knowledge being due to the investigations of Maire (20) 
and of Guillermond (14). Harper, also, has studied several species and 
especially Phyllactinia corylea (19), where he found eight chromosomes 
throughout the life-history. This case is somewhat peculiar, as the chromo- 
somes pair directly after the union of the nuclei, and thus their number 
remains unaltered while their valency is first doubled (in the oogonium) 
and later quadrupled (on the fusion in the ascus). In the same way 
reduction consists not in the diminution of the number of the chromosomes 
but in the halving of their valency. 
In Humaria rutilans (13) the number of chromosomes in the mycelial 
nuclei before fertilization has not been counted ; in the ascogenous hyphae 
(after the pseudapogamous fusion) there are sixteen ; and the same number 
appears throughout the first and second divisions in the ascus and in 
the prophases of the third, when the meiotic reduction and asexual fusion 
are complete. In the third telophase there are only eight chromosomes 
and a second reduction — the brachymeiotic — has thus taken place. 
In Otidea aurantia we were unable to count the chromosomes before 
the fusion in the ascus. The first two divisions in the ascus are, however, 
obviously meiotic, and the chromosomes are then four in number. In the 
third prophase two chromosomes appear, and these divide on the spindle so 
that two pass to each pole. 
In Peziza vesiculosa the nuclei have been investigated by Maire (20) 
and by Guillermond (14), as well as by ourselves. Guillermond finds eight 
chromosomes throughout the divisions in the ascus. Maire also observes 
eight in all three prophases, but he regards these as protochromosomes and 
describes them as fusing to form four in the metaphase. In the late 
anaphase of the first division eight chromosomes reappear and are inter- 
preted by him as representing the prematurely separated daughter- 
chromosomes of the homotype mitosis ; in the second and third anaphases 
he finds only four. 
