Studies in the Genus Pleospora. III

In a previous paper (6) the development of the vulgaris series of this genus, through the 5-septate stage, and of the herbarum series through the 7-septate stage was followed. In a second paper (7), concerned with those species having setose perithecia, several species with more than seven septa were included. The present paper has to do with a somewhat more complicated group of the herbarum series, in which the perithecia are glabrous or merely tomentose and in which the spores have developed beyond the 7septate condition by the insertion of additional transverse septa. Collections are referred to by number, which in turn refers to the list of collections, with detailed data, at the end of the paper. Table I gives data as to microscopical measurements and the pres? ence of tomentum or setae on the perithecia, for each collection, also by number. It is necessary at this point to follow carefully the consecutive insertion of the septa. In a previous paper (6, Fig. 1) a figure was given and a nomenclature for these septa was proposed. A 3-septate spore gives rise to a 5-septate spore (in the herbarum series) by the formation of secondary septa of the vulgaris type in the two central cells, and from such a spore the 7-septate spore is derived by the formation of secondary transverse and vertical septa in each of the end cells. These secondary septa in the end cells commonly take the form of a "Y." The insertion of additional septa in the 7-septate spore, such as found in P. herbarum or P. Armeriae, first appears as tertiary septa in the ultimate or penultimate cell of the lower end of the spore. If the transverse and vertical septa are normally formed this results in four or five septa below, and three above, the central primary septum, giving an 8or 9-septate spore (Figs. 3, 4). If, on the