VIII. c, 1 Broivn and Graff: Fungus Succession 29 
rates of growth, and the disappearance of the mucors and 
Oospora to the presence of microorganisms in the substratum. 
The Coprini appear to be more resistant to the effect of the 
microorganisms although the growth of their vegetative hyphae 
is greatly disminished. 
The deleterious effects which the microorganisms have on the 
grow^th of the fungi under consideration is apparently quite 
similar to their action on vascular plants. The fungi may them- 
selves excrete toxic compounds but the effect of such substances 
must be small when compared with that of the microorganisms. 
SUMMARY 
The succession of fungi on dung cultures in Manila is very 
similar to that reported from temperate regions. Typically it 
consists of Mucors followed by Oospora and in turn by Coprini, 
The Mucors and Oospora disappear in less than ten days while 
the fruit bodies of the Coprini are produced over a considerable 
period. 
The order in which the fungi become visible is probably due 
to their different rates of growth, while the disappearance of the 
Mucors and Oospora is connected with the presence of micro- 
organisms in the substratum. 
The fungi considered may excrete toxic substances, and in all 
probability diminish the food supply, but neither of these 
factors appear to be influential in causing the succession. When 
the mucors are grown on sterilized dung they make a growth 
many times greater than on unsterilized and, moreover, continue 
to appear vigorous until after the substratum is apparently air 
dry. 
The competition of the other fungi considered, causes a restric- 
tion in the growth of the mucors on sterilized dung. This 
restriction is, however, so slight as to apparently exclude the 
r 
idea that such a competition may be the cause of the death of 
the molds in the unsterilized cultures. 
As the substratum dries, all of the fungi cease growing but 
there is no evidence that this factor affects one species sooner 
than the others, and it is certainly not responsible for the death 
of the mucors on unsterilized media. 
