PHACIDIACEAE 2S1 



Pyrenomycetes, and Atkinson (1909) was the first to note that 

 it is a disk fungus which, on closing, looks like a perithecial one. 



Among the Pseudopezizoideae are Fseudopeziza medicaginisy 

 occurring on alfalfa, and P. trifolii, occurring on clovers, each 

 causing leaf-spot diseases. Jones (1919) observed that conidial 

 stages are lacking in both species and that the apothecia may be 

 mature before the leaves are shed. Nothing is known about the 

 events leading to the initiation of apothecia. 



Some mycologists include in the Dermateaceae the white-pine- 

 canker fungus, Tympanis piiiastri [Hansbrough (1936)]. Its po- 

 sition among the Discomycetes is not given, however, by Nann- 

 feldt (1932). It attacks also red pine, producing cankers on the 

 main stem. The apothecia are most common on cankers several 

 years old. The disks occur in clusters, are dull-black, short- 

 stalked, and about 1 mm broad. The ascospores are elongate, 3- 

 to 9-septate, and hyaline; they bud while still within the ascus. 

 Protruding stromata bear pycnidial loculi having tiny conidia 2 

 to 4 by 1 |.i. Very probably this stage will prove to be spermatial, 

 rather than conidial. 



Phacidiaceae. Many mycologists regard the Phacidiaceae as 

 of ordinal rank and as a distinct group intermediate between the 

 Pyrenomycetes and the Pezizales. In this family the genera Rhy- 

 tisma, Keithia, and Cryptomycina are worthy of mention. The 

 best-known representative of Rhytisma, which includes about 

 25 species, all causing tar-spot diseases, is R. acerinum on maples. 

 The conidial stage of Rhytisma belongs to the form Genus Me- 

 lasmia, which may well be regarded as a spermatial stage. Jones 

 (1925) found that the black, innate, conidial stromata shed spores 

 during the summer. Deeply seated within these stromata may 

 be ascogonia, each consisting of an ascogonial cell surmounted by 

 several trichogynal cells and supported below by a more slender 

 filament. Adjacent trichogynal cell walls become perforate, and 

 the nuclei become paired in the ascogone. Ascogenous hyphae 

 arise from the ascogone. Crooks may form at the termini of 

 these hyphae, and the penultimate cell either becomes the ascus 

 or else, if it contains more than a single pair of nuclei, proliferates 

 eventually to form asci. Jones (1925) regarded the conidia 

 (spermatia) as functionless. 



The five known species of Keithia are restricted to conifers. 

 ■Keithia tetraspora occurs on Jiniipenis connmmis, and K. jiinip- 



