THALLOPHYTA: FUNGI 



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uninfected trees. The fungus is usually carried over the winter on dried 

 diseased fruits, called "mummies," that remain on the tree and furnish a 

 fresh source of conidia the following spring. Brown cup-like ascocarps, 

 which are rare, resemble those of Peziza and may be formed early in 

 the season on mummified fruits lying on the ground. 



Summary. The Pezizales are mostly saprophytes but some are para- 

 sites. All have a well-developed mycehum. The asci, accompanied by 

 paraphyses, form a hymenial layer that lines an open, disk-like or cup- 

 like ascocarp, the apothecium. This may be fleshy or leathery and ses- 

 sile or stalked. Some members have well-developed sex organs, the asci 

 arising from the fertilized ascogonium. In other members the asci arise 

 directly from the mycelium, sex organs being absent. 



6. Helvellales 



The Helvellales are related to the Pezizales, being distinguished from 

 them mainly by the form of the ascocarp, which is also an apothecium but 



Fig. 109. Ascocarps of Morchella (A) and Helvella {B), natural size. 



is more highly differentiated. The Helvellales are saprophytes that grow 

 chiefly on humus. They number about 300 species. The best-known 

 genera are Morchella and Helvella. 



Morchella. The common edible morel (Morchella esculenta) has a 

 much-branched mycelium growing in rich humus soil. On it are formed 

 compact masses of hyphae that develop into fleshy ascocarps of character- 

 istic form. These come to the surface of the soil, where they often attain 



