SOUNDS PRODUCED BY PILOBOLUS 259 



3 feet, 1 and Grove found that on one occasion the maximum hori- 

 zontal distance of discharge was 4 feet 10 inches. 2 The largest of all 

 the Piloboli is P. Iwigipes, the stipe of which is usually 2-3 cm. 

 long, whilst the diameters of the sporangium and subsporangial 

 swelling are 0-5 mm. and 1 mm. respectively. When I placed 

 the sporangiophores of this species so that they inclined obliquely 

 upwards at an angle of about 45°, several sporangia were shot 

 more than 5 feet in a horizontal direction, and one to a distance 

 of 6 feet 2 inches. Grove noticed that, when a sporangium strikes 

 one in the face, one can distinctly feel the blow, like that of a 

 small drop of rain, 3 and he called attention to the fact that each 

 discharge is accompanied " by a faint but distinctly audible ' puff,' 

 like the sound of a minute pop-gun." 4 From personal experience 

 with a number of Pilobolus cultures, I am able to confirm Grove's 

 statements both as to feeling the blows of the sporangia and also 

 as to hearing the sound of the explosions. Some horse-dung 

 cultures of Pilobolus Kleinii were carefully watched during the 

 mid-day hours on several successive days. At first I mistook very 

 slight sounds produced involuntarily from my collar and mouth for 

 sounds proceeding from the fungus. However, when these sources 

 of error had been eliminated, I found that it was still possible to 

 detect some, although perhaps not all, of the discharges. On 

 listening very intently in a quiet room, two sounds were to be 

 heard : firstly, a little click as a sporangium left its sporangio- 

 phore, and secondly, a more metallic sound, whenever a sporangium 

 struck the glass side of the crystallising dish which contained 

 the culture. So far as I am aware, the sound of the projectiles, 

 made on striking obstacles, has not hitherto been noticed. Its 

 audibility can be very much increased by a method devised by 

 Mr. F. Wakefield, who was assisting me in the laboratory. One 

 makes use of a drum consisting of a glass funnel, 3 or 4 inches 

 in diameter, across the mouth of which a sheet of thin tissue 



1 Coemans, Monographie du Genre Pilobolus, 1860, p. 39; quoted from Grove's 

 monograph, p. 15. 



- W. B. Grove, Monograph of the Pilobolidse, Birmingham ; reprinted from the 

 Midland Naturalist, 1884, vol. vii. p. 219. 



3 Loc. cit., p. 16. 4 Loc. czt., p. 15. 



