HISTORY OF PILOBOLUS 35 



tropic reaction of Pilobolus to white light and light of different 

 colours {vide infra), grew sporangiophores in the dark and observed 

 the accuracy with which the projectiles struck a small circular 

 window or two such windows. An account of their work was 

 published in 1914. 



In 1921, I^ pointed out that, when discharge of the sporangium 

 takes place, the neck of the subsporangial swelhng just beneath the 

 sporangium is ruptured transversely, the wall of the swelling and 

 stipe contracts elastically, and the cell-sap is squirted out of the top 

 of the swelling, so that the sap carries the sporangium with it through 

 the air. I also stated that Pilobolus Kleinii and P. longipes can 

 both shoot their largest sporangia upwards to a maximum height just 

 exceeding six feet and to a maximum horizontal distance just 

 exceeding eight feet. The experimental evidence upon which this 

 statement rests will be given in the next chapter. 



In 1927, Pringsheim and Czurda,^ in recording their investigations 

 on the ballistics of Pilobolus, again called attention to the fact that 

 a drop of sap expelled from the subsporangial SAvelling travels 

 with the sporangium on its journey through the air, but they 

 were unable to suggest the true form of the projectile during its 

 flight. A solution of this problem will be found in the next 

 chapter. 



The other results of Pringsheim and Czurda's ballistic investiga- 

 tions were summarised by those authors ^ as follows. The horizontal 

 range of Pilobolus is greatest when the sporangiophores are incUned 

 obliquely upwards, and the extreme range observed was about 

 2 metres. The accuracy of the shooting depends on the brightness 

 of the source of light and especially on the range : the greater the 

 distance of the target aimed at, the more pronounced the scattering. 

 With a not too distant disc of light the middle is hit more often than 

 the edge. The speed of the projectile just after discharge, on the 

 average, was found to be 14 metres per second. With the help of 

 a ballistic oscillating pendulum, on the basis of the amount of 



1 A. H. R. Buller, " Upon the Ocellus Function of the Subsporangial Swelling of 

 Pilobolus," Trans. Brit. Myc. Soc, Vol. VII, 1921, p. 61. 



^ E. G. Pringsheim and V. Czurda, " Phototropische und baUistische Problome 

 bei Pilobolus," Jahrh.f. wiss. Bot., Bd. LXVI, 1927, pp. 869-872. 



3 Loc. ciL, p. 900. 



