806 
Journal of Agricultural Research 
Vol. XXXI, No. 9 
Numerous solid media and decoctions were used in the attempt to 
obtain sporulation in the Oregon strain, but none of these gave 
positive results. Hydrogen-ion concentration, temperature, light, 
moisture, and aeration also were varied, but with negative results. 
Possibly these cultures are sterile, but the writer is inclined to think 
that if the right conditions were found they would sporulate. Both 
"the Oregon strain and the Arkansas strain were isolated from asco- 
spores. This, together with the fact that they formed immature 
fruiting bodies at several times, would indicate that they would form 
mature perithecia under the proper conditions. 
The New York strain fruited intermittently, but only after the 
writer had worked with it for several months. When perithecia 
formed they were abundant, but at times the fungus would go for 
several months without fruiting. Then suddenly many of the fresh 
transfers would form perithecia. The uncertainty of perithecial 
formation was still more evident when a large number of plates and 
tubes were inoculated at one time. Although the greatest care was 
exercised to obtain uniform conditions in any one series, there would 
invariably be a few cultures which would not develop perithecia. 
Evidently there is some important factor influencing sporulation that 
has not yet been determined. 
It is reported by Kirby ( 8 ) that all of the New York strains of 
Ophiobolus graminis isolated exhibit the phenomenon of heterothal- 
lism. He states that in order to get sporulation it is necessary to 
grow plus and minus strains together. However, under the condi¬ 
tions of the present work the New York strain, which came originally 
from Kirby, was always homothallic. Single ascospores were 
frequently isolated, and these were germinated and grown separately. 
These single-spore cultures produced mature perithecia repeatedly 
in Petri-dish cultures without the influence of mycelium from any 
other strains. 
Further, when portions of mycelium from a monosporous culture 
were placed on opposite sides oi a Petri dish containing string-bean 
agar, a line of dark-colored mycelium was formed where the two 
mycelia came together, and perithecia were developed along this line 
(pi. 2, A). In this case, two colonies from the same ascospore acted 
in the same manner as mycelia from the so-called plus and minus 
strains reported by Kirby ( 8 ). This experiment indicates that two 
advancing masses of hyphae may change the nature of the substrate 
to the extent that sporulation may be aided, and hr this case induced 
along the line of contact of the colonies. In an environment that is 
not favorable for sporulation, or when weak cultures of the fungus 
are used, two strains may induce sporulation where otherwise they 
would not fruit. It is evident from these results that nutrition or 
the products of metabolism may act as a stimulant for sporulation. 
Possibly this is the explanation of the results obtained by Kirby. 
It is the opinion of the writer that the lack of sporulation of the 
Oregon and Arkansas strains of the fungus in the present studies is 
probably caused by their extreme lack of vigor. Due to their long 
culture on artificial media, with mycelium used for transfers, their 
reproductive ability probably became so low that the various stimuli 
used could not restore it. It seems entirely possible that when other 
factors which influence sporulation are determined these cultures 
might be made to sporulate. 
