MYRIANGIALES 215 



Plectodiscellaceae. — The first type is realized in Plectodiscella Pyri 

 (Woronikhin, 1914) causing a leaf spot of apple and pear in the Caucasus. 

 The young fructifications arise between epidermis and cuticle as a ball 

 of closely intertwined hyphae colored light at the base, but brown on the 

 upper side and at the edges. By the further development of this ball into 

 a pulvinate stroma, the cuticle is ruptured and the young fructification is 

 more or less exposed. In contrast to Kusanoopsis, there are special rind 

 layers (Fig. 138, 3). The underside remains a hyaline, compacter, 

 more-marked pseudoparenchyma than the core of the stroma. The 

 upper side is brown, and develops to a strong, sclerotic, outer layer 

 consisting of polyhedral cells and uniting at the base of the stroma with 

 the basal rind layer. At maturity the outer layer breaks off and after it 

 the stromatic ground tissue, liberating the hyaline 4-celled ascospores. A 

 second species, Plectodiscella veneta (Burkholder, 1917), which causes 

 anthracnose of Rubus in the United States, is noteworthy in that the asco- 

 spores under definite conditions of nourishment germinate first to a sprout 

 mycelium. As an imperfect form, the Melanconiaceous Gloeosporium 

 venetum occurs. 



Fig. 139. — Bagnisiella australis. 1. Section through the stroma from the bark of the host, 

 2. Same, further enlarged. {After Theissen and Sydow, 1915.) 



Saccardiaceae. — In this family, in contrast to the lower Myriangiaceae, 

 is realized the second possibility, the reduction of the number of asci 

 which are no longer formed irregularly in several layers but in a single 

 layer generally lying directly beneath the surface of the stroma and 

 parallel with it (mutatis mutandis as in Myriangium Thwaitesii) . The 

 Saccardiaceae include a whole series of chiefly monotypic genera, as 

 Eurytheca, Saccardia and Anhellia; these are incompletely known and 

 generally have been studied only in herbarium material. One may 

 easily acquire an idea of their structure, however, if one imagines the 

 asci of Kusanoopsis in Fig. 136 to be arranged in a single layer. 



Dothioraceae. — Among the simpler genera, as in Bagnisiella (asco- 

 spores unicellular) and Dothiora (ascospores reticulately septate), we may 

 consider Bagnisiella australis which forms its stromata in rows in the 

 bark of dead branches of Acacia bonariensis in the Argentine; like those 

 of the previous families, they are still indefinite in form, pulvinate, 

 always surrounded with a special, dull black, crust-like rind (Fig. 139, 1). 

 Their new covering behaves like the asci and ascigerous layer. In 

 contrast to most Saccardiaceae, the asci are no longer spherical as in the 



