LIBERATION OF SPORES AND CONIDIA 109 



absorption of water by the intersporal substance causes the 

 liberation of the spores. In Pilobolus, the species of which 

 grow on dung, the entire sporangium is ejected at maturity 

 to a considerable distance, and adheres firmly to the 

 substance it alights upon. If this substance happens to be 

 grass which is afterwards eaten by some animal, the 

 spores germinate in the intestines, and again produce fruit 

 on the dung. 



Several different methods of spore ejection are met with 

 in the Ascomycetes. In many instances the ascus elon- 

 gates considerably, sometim.es to three or four times its 

 previous length, as a preliminary to the emission of its 

 spores. The ascus always remains fixed at the base, and 

 does not break away from its point of attachment, and 

 become pushed upwards by younger asci, as has been 

 stated. The name Ascobolus was given to a genus on the 

 strength of this erroneous idea. In many species belonging 

 to the Pyrenomycetes, where the fruit-case or perithecium 

 is furnished with a minute pore at the apex, through which 

 the spores escape, the asci in the order of maturity elongate 

 until the apex of the ascus reaches the pore, when the 

 contained spores are expelled in successive order. After 

 the emission of the spores, the ascus retracts and undergoes 

 dissolution. In some species of Chaetomium^ Melanospora, 

 Spumatoria, etc., the asci become resolved into mucilage 

 when the spores are mature. This mucilage increases 

 enormously in volume by the absorption, of water, and 

 oozes out of the mouth of the perithecium, carrying the 

 spores along with it, the two often forming a ball or long 

 tendril-like mass at the mouth of the perithecium. 



In other groups of the Pyrenomycetes, as the Peri- 

 sporieae, Nectrioidae, etc., the perithecium is not pro- 



