_ 1906] OVERTON—THECOTHEUS PELLETIERI ~ 457 
will certainly be interesting, therefore, if the yeasts can be shown to 
exhibit like phenomena, but apparently these forms need to be further 
investigated before alternation of generations can be regarded as 
firmly established. 
From the above résumé it will be seen that the doctrine of the 
sexuality of the Ascomycetes has steadily advanced since DEBARy’s 
time, but an immense number of forms remain yet to be investigated 
as to the initial stages of the ascocarp. While much investigation 
has centered on the sexual apparatus, the study of the development 
of the ascospores has by no means been neglected. Within recent 
years a considerable literature has been developed relating to the 
cytology of the ascus. We are concerned more especially with the 
method of spore formation and the phenomena of chromosome 
E. 
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teduction, and the literature of this phase of the subject may be sum- 
marized as follows: 
GJURASIN (’93) first observed mitoses in the ascus of Peziza 
vesiculosa, maintaining that the divisions are karyokinetic and that 
__ the prophases and anaphases take place inside the nuclear membrane. 
__ He discovered well-marked asters but describes no centrosomes. In 
the last or third division the spindles are placed at right angles to the 
length of the ascus. The asters of these nuclei persist for a remark- 
‘ ably long time, and the astral rays, although not connected with the 
_ ‘huclei, are folded back over them. 
: DANGEARD (’94) in studying very young asci of Peziza vesiculosa 
and Borrera ciliaris discovered the two primary nuclei of the ascus, 
which fuse to form the large ascus nucleus. Four nuclei appear in 
the recurved tip of a young ascogenous hypha. By means of trans- 
verse walls the nuclei are so separated that one remains in the end 
cell, two in the penultimate cell, and one in the antepenultimate 
cell. The ascus grows out from the penultimate cell and the two 
nuclei fuse to form the ascus nucleus. This according to DANGEARD 
is a true sexual union. 
HARPER ('05, ’96, 97 ’99, :00, :05) has made the most thorough 
study of the structure and division of the nuclei in a number of Ascomy- 
cetes. He discovered and described the réle of the kinoplasmic 
fibers in the formation of spores. He first counted the number 
Es Of chromosomes in several species. In Pyronema confluens he also 
PAIRS tae eS ae 
