THE PILOBOLUS GUN AND ITS PROJECTILE 55 



nearest to the light. Some of these discharged sporangia were 

 mounted in water on a sUde, and then the individual spores could be 

 seen through the colourless sporangial wall. 



Suspecting that the abnormal development of the fruit-bodies 

 was due to the fumes emitted by the sterilised dung-balls, which 

 were unable to escape from the crystallising disb, I removed the 

 covering plate and set the dish under a large bell-jar. As a result of 

 the change in external conditions, the succeeding crops of fruit- 

 bodies became quite normal in time of development, in the size of 

 the subsporangial swellings and sporangia, and in the development 

 of the intensely black pigment in the sporangial wall. Thus the 

 supposition that the abnormal development of the fruit-bodies in 

 the pure culture of P. longipes was due to gaseous emanations from 

 the horse dung seems to have been well founded. As supporting 

 this view it may be mentioned that fruit-bodies of Coprinus curtus 

 became sterile when subjected to the fumes of fresh horse dung.^ 



In 1876, van Tieghem remarked that he had observed fruit-bodies 

 of Pilobolus oedipus in which the sporangium-wall had failed to 

 blacken, so that, just as in the abnormal P. longipes fruit-bodies 

 described above, the orange-yellow spores showed through the 

 uncoloured sporangium-wall and thus gave to the sporangium as a 

 whole an orange-yellow appearance. ^ 



Van Tieghem,^ also in 1876, gave the name Pilobolus nanus to 

 a minute species, not more than 1 mm. high, which he found on rat 

 dung (Fig. 106, p. 212). This species, according to van Tieghem, 

 differs from all other Piloboh in having a yelloiv (not black) sporan- 

 gium-wall when the sporangium is projected. P. nanus has not 

 been seen again since 1876. For the present, therefore, the possi- 

 bility is not excluded that the yellowness of the sporangium-wall in 

 this species may have been abnormal. 



Species observed. — Among the species of Pilobolus which occur 

 at Winnipeg the following have been identified : P. longipes (Figs. 18 

 and 24), P. Kleinii (Fig. 27), and P. umhonatus nov. sp. (Fig. 105, 



1 These Researches, Vol. IV, 1931, p. 9. 



2 P. van Tieghem, " Troisieme Memoire sur les Mucorin^es," Ann. Sci. Nat., 

 6 86r., T. IV, 1876, p. 342. 



3 Ihid., pp. 340-342, PI. X, Figs. 16-22. 



