278 RESEARCHES ON FUNGI 



further bulging of the septum s'" into it and by its lateral con- 

 traction (stages H to J). 



As the cell c died, a remarkable event was witnessed. In the 

 water, on the surface of which the promycelium was growing, there 

 were a certain number of motile bacteria. These were evenly dis- 

 persed throughout the fluid, but were so few in number as scarcely 

 to attract attention. However, at one particular moment, as shown 

 at H, the bacteria swarmed toward the promycelium and congre- 

 gated upon the surface of the cell c ; while, at that very moment, 

 the cell c was observed to be collapsing (H-I). Evidently, the 

 extremely thin layer of cytoplasm lining the cell-wall of the cell c 

 had suddenly died, in consequence of which the cell-sap was escaping 

 through the cell-wall, the cell itself was contracting laterally, and 

 the escaping sap was stimulating the bacteria chemotactically and 

 causing them to swarm toward the collapsing cell. The bacteria 

 remained at and near the cell-wall of the cell c for only about one 

 minute, and then they moved away again never to return. The 

 dispersion of the bacteria doubtless coincided with a diminution of the 

 chemotactic stimulus caused by the diffusion of the cell-sap into the 

 surrounding medium . As soon as the bacteria had gone away from the 

 cell c, the promycelium had the appearance shown at J in which there 

 are three dead basal cells, a, b, and c, and one living terminal cell t. 



All the stages in the formation of a new basal cell cut off by a 

 new septum have been described, so that we now have a clear picture 

 of the manner in which protoplasmic migration and septation take 

 place in a promycelium. Doubtless these phenomena, as they occur 

 in the sterigmata, the basidiospores, and the mycelium arising from 

 an H -shaped pair of sterigmata or from a basidiospore, run a 

 similar course to that observed in a promycelium. It is probable 

 that further observation will show that protoplasmic migration and 

 septation take place in Polyporus squamosus and in many other 

 fungi in the same manner as in Tilletia tritici. 



Conclusion. — The investigations which have been recorded in this 

 Chapter have led to a new conception of the basidium of the genus 

 Tilletia and to a new mode of inoculating wheat seedlings . The obser- 

 vations made in the course of the work and the chief conclusions arrived 

 at arc summarised in the General Summary at the end of this volume. 



