1918] FITZPATRICK—RHIZINA 215 
papers bearing upon the subject are excellently reviewed by 
HARPER (40, 41), Lotsy (50), OVERTON (56), and GUILLIERMOND 
(37); while more recent literature has been discussed by FRASER 
(29), RamMsBotrom (58, 59), Dopce. (25), and ATKINSON (1). It 
will prove profitable, however, to call attention to the more im- 
portant general problems which are encountered in the investiga- 
tion of the sexual phenomena in this group, and to review briefly 
the results of certain researches which bear directly upon our own 
study of Rhizina undulata. 
The great difference of opinion which exists in the interpreta- 
tion of the nuclear phenomena in the ascogonium, ascogenous 
hyphae, and asci has resulted in general uncertainty as to the real 
essence of sexuality in the Ascomycetes. Certain investigators 
maintain that the fusion nucleus of the ascus is the product of two 
successive nuclear fusions, the first of these taking place usually in 
the archicarp and constituting the sexual fusion, while the second 
occurs in the young ascus and is regarded as vegetative. HARPER 
(41) explains the occurrence of this second fusion in the ascus as an 
attempt on the part of the fungus to maintain the nucleocytoplasmic 
relation or equilibrium in the cell, a large cell such as the ascus 
requiring a large nucleus (DANGEARD 19, HARPER 38, WINGE 67). 
He states further that his researches indicate ‘‘that the fusion of 
the nuclei in the young ascus does not result in doubling the num- 
ber of chromosomes as they appear in the succeeding divisions.” 
Other investigators of this group, however, maintain that the fusion 
nucleus of the ascus is as the result of the two fusions necessarily 
tetraploid, and undergoes during the progress of the three divisions 
in the ascus a double reduction, the haploid number of univalent 
chromosomes being reached in each of the 8 resulting nuclei. FRASER 
(28 Humaria rutilans) and others (FRASER and Brooks 31 Humaria 
granulata, Ascobolus furfuraceus, Lachnea stercorea, FRASER and 
WELSFORD 32 Otidea aurantia, Peziza vesiculosa, and CARRUTHERS 
14 Helvella crispa) state also that the third division in the-ascus 
accomplishes the second reduction by a_ unique process termed 
brachymeiosis. In the later stages of this mitosis, according to 
their accounts, whole chromosomes are pulled toward the poles, 
the number in the telophase thus being reduced to one-half that in 
the seer 
