1 his paper gives a revision of a number of Ascomycetes and it is the result of the examination of herbarium specimens from the mycological collections of the Institute dc Botanica “C. Spegazzini”, La Plata and the “Naturhistoriska Riksmuseet, Botaniska avdelningen”, Stockholm. Ihe following genera and species are discussed: 1. Polystomella pulcherrima Speg. (1888), the type species of the genus Polystomella is identical with Dothidella australis Speg. (1880), the type species of the genus Dolhidella. A number of species, described as Polystomella is placed in the genus Dothidella. The genus Cyclotheca Theiss. 1914 (Syn.; Synostomella Syd.) is closely related to this genus. These genera belong to the Pseudosphaeriales. A number of species, described as ’ ’ ‘ ’’ Polystomella are members of the Parmulariaceae (family of the Dothiorales) and are placed in the genus Campoa Speg. 2. The type species of the genera Munkiella Speg. (1883), Coscinopeltis Speg. (1909) and Apiotrabutia Petr. (1929) are one and the same fungus, which has to be named Munkiella caaguazu Speg. A number of synonyms are given. 3. Ceratostoma usterianum Speg., the type species of the genus Ceratostomina Hansl. (1946) has two-celled ascospores and belongs to the Sphaeriales. 4. Lizonia araucariae Rehm is a typical member of the genus Mycosphaerella. 5. Endodothella coutoubeae (P. Henn.) Theiss. et Syd. belongs to the genus Phyllachora Nits. The type species of the genus Endodolhella is also a Phyllachora. On the other hand, the species with truely two-celled ascospores has to be placed in Stigmochora Theiss. et Syd. 6. The genus Schweinitziella Speg. is reintroduced. The genera Schweinitziella Speg. 1888 (Syn.: Paracesatiella Petr. 1929), Pseudomeliola Speg. 1889 (Syn.: Biotyle Syd. 1929) and Saccardomyces P. Henn. 1904 (Syn.: Ophiotexis Theiss. 1916) belong to the Sphaeriales and are closely related. They are, however, different in morphological and biological characters.