VIII, c, 1 Brown and Graff: F'ungus Succession 27 
fifth and the Coprini on the tenth day. In every case the fungi 
made a much greater growth than in the unsterilized flasks, and 
continued to appear vigorous until after the substratum had 
become air dry. In this case, as in the previous flasks with 
Absidia caeridea, the growth of the hyphae of the Coprini was 
so vigorous that dense felt-like masses were formed, whereas 
these hyphae could not be distinguished in a superficial ex- 
amination of the unsterilized cultures, the presence of the Coprini 
being recognized only by their fruit bodies. 
The total growth of hyphae was many times greater in all 
of the sterilized flasks than in any of the unsterilized ones. As 
in the case of Absidia caerulea, the amount of growth made by 
Mucor racemosa varied inversely to that of the other fungi. 
The greatest growth of Mucor racemosa was obtained when it 
was grown alone, the next best with the small and slow growing 
Oospora, and the poorest with all of the other fungi. The 
growth with Absidia caerulea, Coprinus stercorianus and C. 
plicatilis was about equal and intermediate between that with 
Oospora and with all. It is probable that the total amount of 
growth did not vary greatly in any of the flasks. 
Series similar to the above were run in duplicate in both 450 
and 1,000 cc flasks. The results obtained from these appeared 
to be entirely similar to those just given, except that the indi- 
vidual fungi made a greater growth in the 600 cc than the 450 cc 
flasks and a still greater growth in those holding 1,000 cc. As 
in the case of the preceding series, this was probably due to the 
different amounts of food and air present in the different flasks. 
The experiments with Mucor racemosa show that when this 
species is grown with other fungi there is a sharp competition 
which results in a retardation of its growth but at the same 
time the results do not explain its behavior in the unsterilized 
cultures. In the latter it made a very spindling growth and 
always disappeared in less than ten days vv^hile when grown on 
sterile dung with any or all of the fungi considered the growth 
was many times as great as on the unsterilized media and, 
moreover, continued to be vigorous until the substratum had 
apparently become air dry. 
The experiments, so far reported, would seem to show that 
the succession of the fungi on the unsterilized dung was not due 
to any of three causes which are probably most frequently 
offered in explanation of the successions of higher plants, these 
being; the depletion of nutrient materials by the first plants 
of the succession ; by the plants producing toxins which cause 
