Contributions towards a monograph of Phoma (Coelomycetes) - V. Subdivision of the genus in sections

The differentiating characteristics and nomenciatural history of the nine recognized sections of Phoma Sacc.are listed and displayed in a diagram, tables and keys.Four section names have been formally introduced as new taxa: Macrospora sect.nov., Phyllostictoides (Zherbele) sect.nov., Pilosa sect.nov.and sect.Sclerophomelia (Hé6hnel) comb.nov.Comparative study of numerous species of Phoma Sacc. in vivo and in vitro has finally led to the differentiation of that coelomycetous genus into nine sections.Some of these are artificial, but others represent natural units (compare Boerema, 1985 andVan der Aa et al., 1990).Despite this heterogeneity members of all sections are united in one common characteristic: that the majority of the hyaline conidia remain one-celled in vitro.Conidial septation appears to be a secondary division process; the wall of the septate conidium is not thicker than that of the aseptate conidium (see Boerema & Bollen, 1975).In all cases the first conidium of a conidiogenous cell arises as a thick-walled papilla; see fig. 1, conidiogenesis in Phoma herbarum Westend., the type species of the genus (p.322).The characteristics of the most common sections were discussed in Van der Aa et al. (l.c.); four of them, sect.Phoma sensu stricto, sect.Peyronellaea, sect.Plenodomus and sect.Heferospora have been the subjects of the previously published 'Contributions towards a monograph of Phoma' (