302 RESEARCHES ON FUNGI 



the light Ues of course in this : that it enables the asci to discharge 

 their spores in the direction of the strongest incident rays of light, 

 i.e. in the direction most free from obstacles. In the more or less 

 hemispherical fruit-bodies of Discomycetes like Aleuria vesiculosa, 

 the direction is toward the mouth of the fruit-body. 



The chain of eight spores at the end of an ascus of Aleuria vesi- 

 culosa, as described in Volume I, is held in position by a protoplasmic 

 bridle. The terminal spore in the chain in a hehotropically curved 

 ascus usually has a slope counter to that of the curvature of the 

 ascus, as shown in Fig. 140 (p. 293), while the other spores of the 

 chain are not arranged so regularly. All the eight spores are held 

 together by a string of cytoplasm. The gelatinous meniscus on one 

 side of each spore (Fig. 140) swells up when the spore is shot into 

 water (Vol. I, Fig. 79, H, p. 241) and doubtless, like the similar 

 meniscus on the side of the spores of Ascoholus stercorarius and of 

 Coprinus sterquilinus (Vol. Ill, Fig. 95, p. 227), serves to fasten the 

 spore to the herbage on which it may settle and thus to keep it there 

 until it is swallowed with the herbage by a herbivorous animal such 

 as a horse. There can be but little doubt that the spores of Aleuria 

 vesiculosa, hke those of many other coprophilous fungi, e.g. Piloboh 

 and many Ascoboli and Coprini, are able to pass through the 

 ahmentary canal of a horse unharmed, so that, when excreted 

 within the substance of the sohd faeces, they find a suitable medium 

 in which to germinate. The horse is evidently a very important 

 factor in the dispersion and the maintenance of Aleuria vesiculosa 



as a species. 



In Aleuria vesiculosa, as in the Discomycetes already treated of in 

 this Chapter, an ascus, on discharging its spores, not only contracts 

 but becomes somewhat straighter. In a contracted ascus the 

 operculum is usually symmetrically placed at the end of the ascus, 

 but in a much curved ascus it may be very shghtly inclined toward 

 the shorter and concave side of the ascus. 



In my damp-chamber cultures of Aleuria vesiculosa the cup-shaped 

 fruit-bodies with incurved edges did not contain any mature asci and 

 the spores became ready for discharge only as the fruit-bodies opened 

 out and more or less flattened themselves against the substratum. 

 I gathered an expanded and mature fruit-body from the horse dung 



