170 Journal of the Mitchell Society [March 



would come into contact with colonies of the same strain and of eaeli 

 of the other four strains. 



The production of sclerotia was so:newhat irregular in these plates, 

 but no sign of "mixing" was noted. Sometimes they were most 

 abundant where two colonies, either of the same or of different strains, 

 met ; but this was not at all constant. Often they began developing 

 abundantly at the center of the colony before it had come in contact 

 with the other colonies on the plate. The most abundant develop- 

 ment noted in any case was found where a colony of bacteria was over- 

 grown by the fungus. The variation seemed to be due to irregular 

 food supply and to any irregularity in the surface of the medium 

 which increased the aerial growth of the mycelium. 



While this experiment does not prove the non-existence of plus 

 and minus strains, it does show that mixing of such strains is not 

 necessary for the production of sclerotia. 



germination op the sclerotia 



When mature sclerotia are placed in contact with a suitable me- 

 dium they send out hyphfe from all over the surface without forming 

 any apparent break or crack in the tissues. Each thread arises and 

 pushes out to the surface separately. In new sclerotia such new 

 growth may, probably, arise from any living cell; but in very old 

 sclerotia the cells of the pseudo-parenchyma appear to be dead, and 

 the new growth arises from the cells of the more loose hyphal weft 

 in the center (fig. 4). The new hyphffi are slender and pass lietween 

 the old cells and finall.y pusli or dissolve an opening lietween the cells 

 of the compact outer tissues. 



The cells of the new hyphse are ])inucleate. Whether they arise 

 only from cells that have remained binucleate, or otherwise, has not 

 been determined. 



longevity op the sclerotia 



If kept dry, the sclerotia remain viable for a long time. Some 

 produced in cultures and kept in the culture tubes grew off readily 

 when they were finally transferred to fresh media, when more than 

 two years old. It is not likely that they last very long in contact 

 with moist soil under field conditions. They seem to be very suscep- 

 tible to freezing when wet. 



