STRUCTURE. 



59 



movement, suffices to cause dehiscence, which is generally- 

 followed by a scarcely perceptible contractile motion of the 

 receptacle. 



There is manifestly a succession in formation and maturity of 

 the asci in a receptacle. In the true Ascobolei, in which the 

 sporidia are coloured, this may be more dis- 

 tinctly seen. At first some thin projecting 

 points appear upon the disc, the next day 

 they are more numerous, and become more 

 and more so on following days, so as to 

 render the disc almost covered with raised 

 black or crystalline points ; * these after- 

 wards diminish day by day, until they ulti- 

 mately cease. The asci, after separation 

 from the subhymenial tissue, continue to 

 lengthen, or it may be that their elasticity 

 permits of extension during expulsion. 

 Boudier considers that an amount of elas- 

 ticity is certain, because he has seen an 

 ascus arrive at maturity, eject its spores, 

 and then make a sharp and considerable 

 movement of retraction, then the ascus re- 

 turned again immediately towards its pre- 

 vious limits, always with a reduction in the 

 number of its contained sporidia. 



The dehiscence of the asci takes place in 

 the Ascobolei, in some species of Peziza, 

 Morchella, Helvella, and Verpa, by means 

 of ar- apical operculum", and in other Pezizce, 

 Helotium, Geoglossum, Leotia, Mitrula, &c., 

 by a fissure of the ascus. This operculum bolu * ( Boudier )- 

 may be the more readily seen when the ascus is coloured by a 

 drop of tincture of iodine. 



The sporidia are usually four or eight, or some multiple of 

 that number, in each ascus, rarely four, most commonly eight. 

 At a fixed time the protoplasm, which at first filled the asci, dis- 

 Only in some of the Discomycetes are the asci exserted. 



