General Features 



15 



This heliotropic response of the ascus is most apparent in 

 those species which have comparatively large spores. It is a 

 prominent character in many species of the genus Lamprospora 

 for, in spite of the small size of the plants of this genus, the 

 asci and spores are relatively large, while in some of the large 

 cups of the genus Peziza it is much less apparent because of 

 the small size of the asci and spores. 



If the asci protrude far above the surface of the hymenium 

 the bending in response to light occurs far down on the ascus, 

 while in those that protrude less strongly the bending is nearer 

 the apex, interfering with the bilateral symmetry of the ascus. 



9. Dehiscence of the Ascus 



There are in the Discomycetes several ways in which the 

 ascus may rupture in order to permit the spores to escape. On 



Fig. 8. Methods of dehiscence of the ascus. a, operculate. 

 b, bilabiate, c, inoperculate. 



the bases of the dehiscence of the ascus, they may be classified as 

 operculate and inoperculate forms. By the term operculate we 

 mean the presence of a lid which is quite circular in form and 

 of variable size by means of which the ascus opens (Fig. 8, a). 

 The operculum almost invariably remains attached at one side 

 after the discharge of the spores and often one or two spores 

 may be left behind after the process is completed. The opening 

 formed by the rupture of the ascus will be here designated as 

 the ascostome. 



The inoperculate method of dehiscence consists of a simple 

 rupture which leaves the margin of the ascostome toothed and 

 ragged after the spores have been ejected (Fig. 8, c) but with no 

 sign of an operculum or lid. 



