16 The North American Cup-Fungi 



A third type of dehiscence is known among a few of the cup- 

 fungi and is referred to as the bilabiate method (Fig. 8, b). 

 This consists of the rupture of the ascus by means of a transverse 

 sUt across the top so that the ascostome gaps open like a fish's 

 mouth after the expulsion of the spores. This is characteristic 

 of the genus Streptotheca and a few allied forms. Roughly this 

 is considered as a modification of the operculate method and 

 those forms which show this type of dehiscence are classed with 

 the Operculates since otherwise they show more affinities with 

 this group than with the Inoperculates. 



10. Significance of the Mode of Dehiscence 



The operculum was first observed by H. M. Crouan in some 

 species of Ascoholiis but he had not seen it in the larger Pezizaceae. 

 It was at first regarded as one of the characters of Ascobolus 

 and some species in which the operculum had been noted were 

 transferred to Ascobolus for this reason. This is no longer 

 looked upon as a generic character and species originally placed 

 in Ascobolus are now treated as Ascophanus, Humarina and 

 Lamprospora, the genus Ascobolus being used in a more restricted 

 sense. 



The inoperculate method of dehiscence was also observed by 

 Crouan but no great importance was attached to it at that 

 time. Later M. E. Boudier found the asci of many of the larger 

 Pezizaceae to be operculate and he first suggested dividing the 

 Discomycetes into two groups, the operculate and the inopercu- 

 late forms, and proceeded to show that the presence or absence 

 of the operculum in the ascus was a character of fundamental 

 importance. It is so regarded in this work and, so far as the 

 writer knows, by all modern students of cup-fungi. 



As pointed out by Boudier this seems to be a very natural 

 division and there is little difficulty in determining the method 

 of dehiscence although few workers at that time took the trouble 

 to mention it. Boudier also made, in the opinion of the writer, 

 a very important observation when he mentioned that in most 

 cases the operculum was horizontal or at right angles to the 

 long axis of the ascus while in a few species it was oblique. 



That the separation of the cup-fungi into the Operculates 

 (Operculatae) and Inoperculates (Inoperculatae) is a natural 

 division and morphologically sound is indicated by the fact 

 that associated with this character are certain other morpho- 



