1918] FITZPATRICK—RHIZINA 219 
ditions a form which he stated to be Pyronema confluens and was 
able to develop normal or rudimentary antheridia or to suppress 
them entirely, while the ascogonia developed normally under all 
conditions. DANGEARD (22) found in what he regarded as the 
same species that even in cases in which the antheridium fuses with 
the trichogyne the male nuclei degenerate in situ, and fail to enter 
the ascogonium. Brown (10, 13), working with a strain which he 
has named Pyronema confluens var. inigneum, found that the 
ascogonia and antheridia fail to fuse, and states that only one 
nuclear fusion, that in the ascus, occurs in the life cycle. He also 
examined the parent species, and states that in it he found migra- 
tion of male nuclei into the ascogonium. Pyronema confluens var. 
inigneum, according to the account of Brown, differs from the 
parent species physiologically also in that it grows freely upon an 
unsterilized substratum. The variation in the accounts of the 
different workers who have examined this species would seem to 
show that in this form the degeneration of the antheridium is now 
taking place. On account of the small size of the nuclei the 
demonstration of fusion in the ascogonium, however, is extremely 
difficult and it is possible that two investigators might reach a 
different conclusion from the examination of a single set of 
slides. 
The writer feels that neither in Pyronema confluens nor in any 
other Ascomycete have two successive nuclear fusions in a single 
life cycle been conclusively demonstrated. It is evident that we 
cannot depend upon a critical examination of the nuclear divisions 
in the ascus to tell whether or not one or two fusions have occurred, 
since here also a fundamental difference in interpretation exists. 
Although Fraser and her co-workers figure and describe brachy- 
meiosis in several species, HARPER and others find the chromosome 
number remaining constant throughout the three divisions in the 
ascus. 
Summary . 
1. The sexual process has not heretofore been studied in any 
member of the Rhizinaceae. The examination of Rhizina undulata 
Fries is therefore of considerable interest. 
