Xchraskti Forest Fungi. II 83 



seen that the surface is rather uneven, rendered so by the com- 

 plex of low ridges that gives a peculiar wrinkled appearance to the 

 surface of the spots. By the following spring there have devel- 

 oped in the sclerotial masses many complex apothecia which 

 rupture the surface along the ridges in the black wrinkled surface. 

 These openings appear as very fine elongated fissures, so that at 

 this time the surface becomes cut and lacerated. The asci are 

 club-shaped with long stalks, and contain eight long, narrow, 

 pointed spores. 



When this parasite developes to the degree that character- 

 ized its activity in certain parts of the state during the season of 

 1910 it certainly decreases the efficiency of the photosynthetic 

 machine to a considerable degree. Many Very badly infected 

 trees were found in Cass County. On some of these considerably 

 more than one half of the leaf area was covered by the spots of 

 this organism, and the total extent of infection was of course 

 much wider than the spots indicated. The above species is very 

 common on Acer saccharinum L. in eastern Nebraska. 



Other species of Rhytisma, such as R. salicinum (Pers.) Fr. 

 on various species of SalLv, are quite widespread although not so 

 conspicuous as the above species since willows are not so com- 

 monly cultivated as maples and the spots on willows are not so 

 prominent nor so large as those on the maples. 



Exoascaccae: 



Within our borders this group of fungi is important mainly 

 as producing disease in certain wild and cultivated fruit trees 

 belonging to the Rosaccae. The family is composed largely of 

 parasitis species which live in the intercellular air spaces of 

 Drupaceous hosts. The commonest, and most widespread species 

 are E.roascus deformans (Berk.) Fuckel, causing the "leaf curl" 

 of the peach, and E. prnni Fuckel, causing the so-called "plum- 

 pockets" on varieties of plums. They are consequently of little 

 importance to the forester in Nebraska. However in other re- 

 gions certain species very commonly produce deformities of the 

 leaves and fruits of forest trees. A number of species are known 

 that possess a perennating mycelium, while in the greater num- 

 ber of the species in the family all of the mycelium is used up in 

 the formation of asci. The asci are formed at the ends of hyphae 

 just beneath the epidermis of the host. The asci are usually 

 exposed at maturity and in considerable abundance so that a 

 powdery nature is given to the surface of the infected portions. 

 Some of the perennial species form "witches' brooms" on species 

 of Abuts. 



