186 ANNALS OF THE MISSOURI BOTANICAL GARDEN 



[Vol. 6 



of the fungi the plates were cut into small squares (about 8 mm. 

 square), which were used as inocula. Agar plates made in a 

 similar manner were each inoculated with three of the fungi in 

 such a way as to have all possible combinations of each fungus. 

 From these plates the reciprocal influence of growth was de- 

 termined. The results of the plate cultures are shown in 

 table i. 



The outstanding feature of these results is the preponderance 

 of inhibition of growth of one fungus before and after contact 

 with another. In some cases this inhibition took place when 

 the two colonies were still a considerable distance apart; in 

 others only when they came into close proximity with each other. 

 Figures 5 and 2 respectively of pi. 4 illustrate this feature. In 

 those cases where inhibition occurred after contact the condition 

 is shown by a straight line unless one fungus has a much more 

 rapid growth than the other. Figures 8 and 11 illustrate this 

 point. It often happened that one fungus on the plate grew 

 much more rapidly than the other two, cutting off contact be- 

 tween them. Therefore, all possible combinations could not be 

 recorded in the table. 



There were not as many instances where one fungous colony 

 grew over another as there were of inhibition of growth. In some 

 cases of the former type one colony was completely covered, and 

 the shape of the submerged colony determined that of the 

 colony of the invading fungus, as, for example, in the case of 

 Pleurotus sapidus growing over Aspergillus glaucus and A. 

 Sydowi (see figs. 3 and 6). In these cases the growth of 

 Pleurotus sapidus is greatly accelerated as soon as it reaches the 

 colonies. In other cases the growth of the invading fungus was 

 comparatively slow, as, for example, when Pleurotus sapidus 



fig. 9). At first both of 



invaded 



mutually inhibited and 



gradually advanced. A peculiarity of this special case is the 

 fact that the spores of Aspergillus niger disappeared in the in- 

 vaded section. It could not be determined whether these spores 

 germinated or were digested. 



When 



of 



