HELIOTROPISM OF ASCI IN DISCOMYCETES 295 



hemispherical fruit-body {cf. Fig. 140, A) were mounted in water 

 and then a drop of iodine was run under the cover-glass so that it 

 came into contact with the outer surface of the hymenium. The 

 wall of the free end of each mature and projecting ascus turned 

 blue as it absorbed the iodine, and then the ascus suddenly shot 

 out its eight spores into the surrounding fluid. All the asci in 

 sections of one fruit-body discharged their spores within a few 

 seconds, so that the iodine caused the phenomenon of puffing to 

 take place in a watery medium. Whilst the discharge of the spores 

 was taking place, it was easy to see that each ascus shot away its 

 spores in the direction in which it was pointing, i.e. at an angle of 

 about 45° to the outer surface of the hymenium. This direction of 

 discharge, had the asci been left undisturbed in their fruit-body 

 under aerial conditions, would have enabled the asci to shoot their 

 spores upwards and through the fruit-body's mouth. 



If a piece of the wall is quickly taken from the side of a mature 

 fruit-body of Aleuria vesiculosa which has been enclosed for some 

 time in a glass case, and is held horizontally in the air until it pufEs, 

 since the asci are inclined in the direction of the rim, the spores 

 should be discharged into the air in the general direction of the 

 rim and the cloud of spores should be seen thus travelling with the 

 naked eye. Unfortunately, when I wished to make this experiment 

 with Aleuria vesiculosa, no more suitable fruit-bodies of that species 

 were available ; but the proposed experiment came ofE quite success- 

 fully with the very similar fruit-bodies of Galactinia badia (Fig. 149, 

 p. 308) : the spores were shot toward the rim of the piece of fruit- 

 body in a cloud at an angle of about 45° with the outer horizontally- 

 placed surface of the hymenium. 



A fruit-body which developed in the large damp-chamber in the 

 laboratory was abnormally wrinkled and flattened out in the manner 

 shown in the transverse section in Fig. 142, A ; and it happened to 

 be so arranged that it faced the incident light. I very carefully 

 examined the central convex ridge both in radial-longitudinal and 

 m surface sections, and I found that the asci at the top of the ridge 

 were straight and faced the light while those on the sides were 

 curved upwards so that they also faced the light, i.e. that all the 

 asci on the convex central ridge were pointing toward the light 



