218 PHYLUM VII. CARPOMYCETEAE 



from 7 to 12 centimeters high. It is edible and bears 

 the name of Mushroom in the central United States. 



350. The Plum -pocket fungus (Exoascus), which dis- 



torts the young plums in spring and early 

 summer, is a greatly reduced parasitic sac 

 fungus (Order EXOASCALES). Here the plant 

 consists of delicate threads which penetrate 

 the tissues of the plum, eventually producing 

 on ^^ e sur ^ ace poorly developed asci which are 

 not aggregated into cups. 



351. Two additional orders of lichens the Slit Lichens 

 (Graphidales) and Closed Lichens (Pyrenolichenes) are 

 abundantly represented by species of Arthonia, Graphis, 

 and Endocarpon. In the first order the apothecia are so 

 nearly closed as to leave only a narrow slit, and in the 

 second the asci are wholly enclosed, the fruits being peri- 

 thecia, with only a minute pore or none at all. 



352. The Slit-fungi (Order HYSTERIALES), are to be 

 associated with the Slit Lichens, and may be illustrated 

 by the Black Slit-fungus (Hystero- 



graphium) whose saprophytic fila- 

 ments ramify through bark or old 

 wood and eventually produce small, 

 black, narrow, elongated, sessile 

 apothecia, whose edges approximate, 

 leaving only a narrow slit. Each 

 ascus contains eight muriform, 

 elongated spores, and the asci are intermixed with 

 branched paraphyses. 



THE CLOSED FUNGI (ORDER PYRENOMYCETALES) 



353. The plants of this order are parasitic or saprophy- 

 tic filaments, and their spore-fruits, which are simple or 

 compound, are usually hard and somewhat coriaceous. 



