Development of the Ascostroma in Pleospora Armeriae of the Pleospora Herbarum Complex

The binomial Pleospora herbarum (Fr.) Rab. has been used in a very broad sense for a large species complex having 7-septate spores, and a few points of clarification are necessary to fix the position of the isolations used in this study. In a previous paper (Wehmeyer 1953) the writer stated that all type collections of the basonym Sphaeria herbarum examined were not of the genus Pleospora and it was proposed that Rabenhorst's type of Sphaeria allii be taken as the lectotype of the genus Pleospora. Since that time, Dr. D. M. Henderson has thoughtfully sent the writer a slide made from the copy of Fries' type exsiccatus (Scler. Suec. 38) of Sphaeria herbarum deposited in the Royal Botanic Garden at Edinburgh. All previous copies of this exsiccatus have shown only a Phoma, but his copy bears numerous perithecia of a Pleospora with spores which are identical with Rabenhorst's fungus on Allium. This material can, therefore, be considered as the lectotype of Sphaeria herbarum and of the genus Pleospora, and the binomial Pleospora herbarum (Fr.) Rab. remains legitimate. In a previous account (Wehmeyer 1952) it was pointed out that Rabenhorst's exsiccatus of P. herbarum (Herb. Myc. II, 547a) has comparatively small, thin-walled perithecia which collapse in a pezizoid fashion with age, and spores measuring 25-34 X 9-11.5 p. The general conception of the P. herbarum perithecia has been that of a large thickwalled sclerotic type.