218 PHYLUM VII. CARPOMYCETEAE 
from 7 to 12 centimeters high. It isedible 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 Exoascatss). Here the plant 
consists of delicate threads which penetrate 
the tissues of the plum, eventually producing 
Fra. 100. —_ on the surface poorly developed asci which are 
not aggregated into cups. 
351. Twoadditional 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 Hysteriaues), 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 y 
apothecia, whose edges approximate, 
leaving only a narrow slit. Each py, 101—Hysterogra- 
ascus contains eight muriform, as 5 
elongated spores, and the asci are intermixed with 
branched paraphyses. 
Tue Ciosep Funat (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. 
