vm, c, 1 
Brotvn and Graff: Fungus Succession 
23 
accompanied by a species of Pilobolus. In a few cases species 
of Botrytis and Sordaria appeared along with Oospora, while 
other species of Coprinus sometimes took the place of those 
previously mentioned. The succession described in detail thus 
appears to be characteristic of what may be expected to occur 
in Manila and was therefore made the basis of further work. 
Pure cultures of each of the five fungi were kept growing on 
agar, the fungi being transferred to fresh tubes as often as 
was necessary to keep them in good condition. All inoculations 
made in the experiments were from these pure cultures. The 
dung used was obtained from the stable of the Bureau of Science 
and so should have been substantially similar in all cases. 
Since the mucors were the first of the fungi both to appear 
and disappear the experimehts were directed largely toward dis- 
covering the cause of their early death. The first question con- 
sidered was the possibility of this having been due to toxins 
which the plants themselves might have excreted. In order to 
test this six cakes of dung were placed in each of four covered 
glass dishes. The dishes and dung were then sterilized to kill all 
organisms contained in them. This was accomplished by heat- 
ing in an autoclave for fifteen minutes at 120° under a pressure 
of one kilo. On the 7th of February two dishes were inoculated 
with Mucor racemosa and two with Ahsidia caerulea. On the 
third day after inoculation the growth of the mucor was in 
every case much greater in all dishes than that which had oc- 
curred in any of the unsterilized cultures and continued to be 
healthy for eight weeks. After this the substratum dried out 
and they gradually ceased growing but appeared to be alive at 
the end of another month. Twelve other sterile cultures were 
run at various times in Erlenmeyer flasks the bottoms of which 
were covered with a layer of dung 2 cm deep. These gave 
results very similar to those just described. It is to be noted 
that the mucors on the sterile dung were still alive even after 
the substratum had apparently become air dried while those on 
unsterilized dung always disappeared completely in less than 
ten days. This, together with the much more vigorous appear- 
ance of the former, would seem to show that the death of the 
molds in the original cultures could hardly have been due to 
toxins which they excreted. It would also appear that these 
facts exclude the idea that the mucors could have used all of 
the food material which was suitable for them. 
The results in the original cultures could moreover not have 
been due to differences in the amount of water in the substratum. 
