HELIOTROPISM OF ASCI IN DISCOMYCETES 271 



violet spores. Dodge gives the diameter of the fruit-bodies as 

 0-5-2 -7 cm. 



Observations made on artificial cultures in the laboratory 

 showed that the asci of Ascobolus magnificus, like those of other 

 Ascoboleae, are positively heliotropic. When the hymenium is 

 illuminated from above, as indicated in Fig. 130, A, the asci grow 

 perpendicularly upwards and the axis of the apical end of each 



Fig. 129. — Ascobolus magnificus. Young fruit-bodies grow- 

 ing on sterilised horse dung in a glass jar. Spore - 

 discharge has not yet begun. Photographed by B. O. 

 Dodge. Natural size. 



ascus remains parallel to the incident rays of light ; and, when the 

 hymenium is obliquely illuminated, as indicated in Fig. 130, B, the 

 asci make a growth curvature until the axis of the aj)ical end of 

 each ascus becomes parallel to the incident rays of light. 



The asci of Ascobolus magnificus, like those of A. immersus and 

 other Ascoboleae, are, as compared with typical Pezizaceae such as 

 Aleuria vesiculosa and Oalactinia badia, remarkably protuberant 

 (c/. Fig. 130 mth Figs. 140, p. 293, and 147, p. 306). Almost one- 

 third of a ripe ascus of Ascobolus magnificus projects freely into 

 the air, and it is this terminal portion of the ascus which bears the 



