i io TEXT-BOOK OF FUNGI 



vided with an aperture for the escape of the spores ; their 

 liberation in such instances being effected by rupture of 

 the perithecial wall, caused by the swelling of mucilage. 



In the Discomycetes, where the numerous asci are 

 placed vertically and closely packed, their apices, along 

 with the tips of the paraphyses, forming the surface of the 

 cup, all the spores in an ascus are ejected simultaneously. 

 In Ascobolus the spores are individually surrounded by a 

 colourless layer of mucilage, or the whole of the spores in 

 an ascus are bound together by mucilage, as in Saccobolus. 

 Such spores are ejected with considerable force, and 

 become firmly fixed to the substance on which they 

 alight, by the mucilage which sets hard and is insoluble in 

 water after exposure to the air. Those spore-masses that 

 alight on grass or other herbage eaten by animals, either in 

 a living or dried condition, germinate in the alimentary 

 tract, and produce fruit on the dung. 



In other species, where wind is the dispersing agent, the 

 spores are liberated in clouds at intervals. This process, 

 which is termed puffing, is due to the simultaneous dis- 

 charge of the spores from numerous asci at the same 

 moment. Various species of Peziza, Helvella, and Bul- 

 garia exhibit this phenomenon. De Bary pointed out that 

 puffing does not occur when the fungi are growing in a 

 very damp and still atmosphere, as under a bell-jar ; but 

 that puffing commences as soon as such fungi are removed 

 into a dry atmosphere. This is considered to be due to 

 the sudden loss of water altering the state of tension in 

 each ascus, and not to shrinkage and contraction of the 

 entire hymenium. This is probably the true explanation 

 of the phenomenon, as I have observed that puffing can be 

 brought about in Peziza vesiculosa by concentrating the 



