EMERSON: MACROPHOMA AND DIpPLopiAa 553 
similarity of their pycnidia. So it was with no little pleasure that 
pycnidia were noticed on two seperate cultures, one pure Macro- 
thoma and the other pure Diplodia. Cultures on cocoanut pith 
started January 11th showed on January 23d pycnidia with an 
abundance of Macrophoma spores in each of the cultures, and on 
February 12th there was obtained from the same pycnidium both 
unicellular hyaline Macrophoma spores and bicellular brown 
Diplodia spores. This is the average time that it takes a pure cul- 
ture on the most favorable medium to develop, namely 10-12 days 
for pycnidia with Macrophoma spores and 12-18 days more before 
Diplodia spores are also abundant. There may be a slightly 
earlier development of the two-celled spores in the pycnidia of 
cultures from Diplodia spores than those from Macrophoma, but 
in general there is no difference in appearance of mycelium, size, or 
shape of spores or pycnidia. There certainly seems to be no 
doubt that the unicellular white Macrophoma spores in the pycnidia 
are simply the immature forerunners of the mature Diplodia spores. 
In microtome sections of the leaf with the fungus growing on it 
from a culture five weeks old, the cells near the pycnidium seem 
much disorganized by the intercellular hyphal threads, being con- 
tracted into irregular darkly-stained masses and the cell-walls 
being difficult to trace. This affected area extends along the 
lower part of the leaf to some distance on either side of the 
pycnidium, but does not go through to the upper side. 
Material for microtome sections was put into weak Flemming’s 
Solution to kill and fix. It was then washed in water, dehydrated, 
and imbedded in paraffin. Some sections were mounted in 
Canada balsam without any staining, but the Macrophoma spores 
Proved to be almost invisible and some of the Diplodia spores too 
dark. As the pycnidia are very black an attempt was made to 
decolorize the sections by putting them into hydrogen peroxide 
and alcohol for about five hours. After washing they were stained 
in saffranin, gentian violet and orange gentian and mounted in bal- 
sam. This combination stains the J/acrophoma spores orange 
and the rest of the pycnidium brown, but care must be taken not 
to overstain. The most satisfactory staining method was saffranin 
ten minutes, Delafield’s hematoxylin five minutes, washing out 
€Xcess of scain with acidified alcohol, and mounting in balsam. In 
