58 Wisconsin Academy of Sciences, Arts, and Letters. 
eight when the first wall is formed. In the germ tube of 
Eypholoma the nuclei divide independently as was shown by the 
appearance of a single nucleus dividing in one of the germ tubes. 
A septate mycelium is formed in Ilypholoma, the cells of which 
contain from one to nine or ten nuclei. The mycelial cells of 
Coprinus frequently contain as many as fifteen nuclei. Lateral 
branches are formed in both Eypholoma and Coprinus, the cells 
of which have a single nucleus. The cells are short and separate 
from each other readily. In Eypholoma these cells germinate 
forming a normal mycelium, thus proving conclusively that they 
are oidia. In Coprinus the cells did not germinate but their 
similar origin and structure indicate that they also are oidia. 
Apparently after a varying period of growth hyphae are 
formed which have regularly two and only two nuclei in their 
cells. In the forms studied this association in pairs does not 
• , # r ^ 
arise at any otherwise differentiated time or in any special 
structure. 
We must remember as described above in Coprinus that binu- 
cleated cells were sometimes formed very near the spore, the 
main hyphae at a distance of two or three cells from the source 
of its origin having regular binucleated cells. In other cases 
special branches having binucleated cells were formed. When 
these branches arise from the uninucleated cells they probably 
receive a single nucleus which immediately divides. This divi¬ 
sion is not followed by a cross wall separating the two nuclei 
and thus the first binucleated cell is formed. If the branch hav¬ 
ing binucleated cells originates from a multinucleated cell it may 
receive two nuclei from the parent cell or it may receive a single 
nucleus that divides to form the second nucleus. 
The hyphae with binucleated cells branch frequently and may 
develop immediately into a carpophore. This method of carpo¬ 
phore formation has been described for Coprinus ephemerus . 
The cells of the young carpophore are always binucleated and a 
series of binucleated cells extends to the formation of the 
hymenium. Thus the basidium with its two nuclei is the last 
of a long series of binucleated cells. That these two nuclei have 
maintained distinct lines of descent from the first cells with 
two nuclei occurring in the mycelium is not certain. I have not 
