242 RESEARCHES ON FUNGI 



the third, and so on. It seems to me very probable that it is 

 the considerable differences in the initial velocities given to the 

 different spores upon their discharge which is the chief factor in 

 separating the spores from one another during their upward flight 

 into the air. There is, however, another factor which must be 

 concerned with the breaking up of the ascus jet, namely, surface 

 tension. 



It has been found both by mathematics and experiment that 

 the equilibrium of a free cylinder of any liquid, under the in- 

 fluence of surface tension only, becomes unstable as soon as the 

 length exceeds TT times the diameter ; and it is regarded as a 

 necessary consequence of this that such a cylinder, if once realised, 

 will spontaneously split into as many equal and equidistant spheres 

 as TT times the diameter is contained in the length. 1 



Thus if n be the number of drops, 



I the length, and 

 d the diameter of the cylinder, 



the law of segmentation is expressed by the formula 



From this formula we can calculate that, if the length of a 

 cylindrical column of fluid is twenty-five times the diameter, the 

 column will break up under the influence of surface tension into 

 eight separate drops. It seems to be a simple inference from this 

 that, if in a minute cylinder of this kind there were placed eight 

 equidistant solid spheres with diameters equal to the diameter 

 of the cylinder, then the cylinder would break up in such a 

 manner that each spherical body would become separated from 

 its neighbours and enclosed within a film of fluid. The ascus 

 jet must be at first essentially a cylindrical liquid column con- 

 taining solid oval nuclei at intervals. Probably the spores are 

 ejected end-wise through the contractile ascus mouth so that 

 they come to have their long axes in the same direction as the 

 long axis of the jet. As the jet becomes elongated, owing to its 



1 A. M. Worthington, "On the Spontaneous Segmentation of a Liquid An- 

 nulus," Proc. of the Roy. Soc., vol. xxx., 1879-80, p. 49. 



