Culture Studies in the Genera Pleospora, Clathrospora, and Leptosphaeria. II

SUMMARY

1.	Statistical analyses of ascospore lengths in samples derived from different perithecia of a single culture each of Pleospora njegusensis, of Clathrospora diplospora (“normal” ascospore size), and of a species referred to as a “large-spored variety” of C. diplospora indicated that ascospores of P. njegusensis vary in numerous different patterns of length and that ascospores of each, of the isolates of “C. diplospora” vary in a decidedly smaller number of different length-patterns.
2.	Ascospore-size data and statistical data on ascospore length indicated that the two fungi referred to as different strains of Clathrospora diplospora are two distinct species of Clathrospora.
3.	Production of mature perithecia by different strains of Pleospora and Clathrospora appeared to be positively influenced by the physical factors of room temperature during the initial period of growth, of low temperature during the remainder of the growth period, and of the total growth time.
4.	The number of mature perithecia produced by individual isolates on Leonian's agar often was characteristic for a species.
5.	The cultural characters of separate isolates of single species often were different: a. Pleospora ambigua: one isolate produced mature perithecia in culture; two other isolates did not. b. Pleospora njegusensis: the isolate from ascospores of one collection produced mature perithecia in culture; a similar isolate from a second collection did not. c. Pleospora trichostoma: two distinct growth types were produced by different single-spore strains; however, no differences in the type or quantity of perithecial production were found in any of the cultures. d. Clathrospora diplospora: strains derived from ascospores from two different collections produced mature perithecia in culture; a third strain derived from ascospores from the same collection as one of the perithecial strains produced only conidia in culture.

The author welcomes this opportunity to express his continuing gratitude to Dr. L. E. Wehmeyer for guidance throughout the course of these studies and to Dr. A. H. Smith for editorial criticism of the manuscript.