22 'The Philippine Journal of Science im 
success of the latter plants may be due to the fact that the 
first have altered the soil in such a manner that it will support 
them. Many writers have advocated the view that when one 
plant grows on a soil for a considerable length of time it removes 
certain nutritive substances to such an extent that it is no longer 
able to make a vigorous growth. Others have held that plants 
excrete substances which are toxic to the species which excretes 
them, but may not produce harmful effects in other plants. 
These last two hypotheses have naturally frequently been used 
to explain the same phenomena. Another factor which might 
affect successions of either vascular plants or fungi is the growth 
of microorganisms in the soil. In the case of the succession 
under consideration it is also necessary to consider the possible 
effect of the drying out of the substratum. The object of the 
present paper is to decide which, if any, of the above hypo- 
theses will furnish a solution of the cause of the succession of 
fungi on dung cultures. 
The work here reported was carried on at the Bureau of 
Science, Manila from January to June, 1912. 
EXPERIMENTATION 
w 
On the 29th of January a collection of horse dung was made 
from the streets of Manila. Twenty cakes were placed in the 
sun and left until their outer surfaces became slightly dry, after 
which they were distributed, five in each of four covered glass 
dishes. By the next day there were signs of two mucors which 
later proved to be Miicor racemosa Fres., and Absidia caerulea 
Bain. On the second day there was a fair growth of both molds 
and slight signs of Oospora sp. By the third day the two mucors 
had made their maximum growth which, however, was not very 
vigorous. The Oospora continued to increase in abundance for 
several days longer. On the fourth of February, at the end of 
six days, Coprinus stercorianus Fr. and C. plicatilis Fr. appeared 
in the cultures. By this time the growth of the mucors had 
decreased markedly and they died out three days later. The 
Oospora disappeared a few days after the molds, while the fruit 
bodies of the two species of Coprinus continued to be produced 
for two months, which was as long as the cultures were kept. 
During the latter part of this period other fungi appeared in 
the cultures but in minor quantities. 
Twelve other cultures were run with dung obtained from the 
stable of the Bureau of Science. The results in all cases were 
essentially similar to those just described. In some of the dishes 
only one of the mucors appeared, while in one, the two were 
