2 8o TEXT-BOOK OF FUNGI 



opening for the escape of the spores being situated at the 

 apex of the neck. Sometimes these perithecia are isolated, 

 each one being an entity, as in Sphaeria. In other 

 examples, as Xy/aria, numerous perithecia are embedded 

 in the periphery of a more or less fleshy stroma, their 

 stomata for the escape of the spores opening on the free 

 surface of the stroma. This structure may be considered 

 as a compound Sphaeria^ in the sense of numerous peri- 

 thecia (independent plants) in Sphaeria, being grouped 

 together on a stroma, the whole forming a plant, in 

 Xylaria. In some genera, as Nectria, the entire sequence 

 from where one perithecium constitutes a plant, to others 

 where numerous perithecia embedded in a stroma represents 

 an individual, is met with. In other genera, as Gnomonia, 

 not uncommon on dead hazel leaves, the neck of the 

 perithecium is very much elongated and hair-like ; whereas 

 in Nectria the neck is entirely suppressed, and the minute 

 ostiolum is situated at the apex of the more or less 

 globose perithecium. In some cases the surface of a free 

 perithecium is minutely downy, at others covered with 

 stout, spine-like structures, whereas in the Perisporieae the 

 perithecia often bear much - branched, highly specialised 

 hyphae called appendages, the function of which is not 

 known. 



In the Discomycetes the ascophore is typically shallowly 

 cup-shaped, with or without a distinct stem. The asco- 

 phore or cup, as it is often called, usually has the margin 

 strongly incurved when young, but this gradually expands, 

 exposing the circular hymenium or disc. The only good 

 example of a stroma in the Discomycetes is met with in 

 the genus Cyttaria, where the general appearance of the 

 fungus is that of a morel (Aforchella), but in Cyttaria 



