A SEPTORIA DISEASE OP EUPHORBIA PEPLUS L. By Dorothy E. Shaw, Faculty of Agriculture, University of Sydney. (Plate i; one Text-figure.) [Read 28th March, 1951.] Synopsis. A Septoria disease of Petty Spurge is described, and the Australian distribution is given. The cultural characteristics and morphology of the causal organism are described. The results of investigations concerning the host-parasite relations, tlie longevity of the spores, the search for the perfect stage, and pathogenicity tests with other plants are given. The literature describing species of Septoria parasitizing species of Eupliorhia is examined, and the name S. pepli, n. sp., is proposed for the causal organism. Introduction. A leaf and stem spot disease of EnpTiorhia peplus L., caused by a species of Septoria, was pointed out to the writer by Professor W. L. Waterhouse in 1947. He had bad it under observation for some time, and noted that infection on Petty Spurge was quite widespread around Sydney. At his suggestion an investigation of the disease was carried out, with particular reference to the host range, as some serious diseases of economic plants are caused by species of Septoria. Economic Importance. Euphorbia peplus L., Petty Spurge, native to Europe and Asia, occurs on the New South Wales coast and tablelands, and in Queensland, Victoria, South Australia and Western Australia, as recorded by Hurst (1942). She listed its reputed medicinal and photographic properties, but to the writer's knowledge it is not used commercially in Australia. Hurst also recorded it as containing a poisonous principle, euphorbin. It is a weed of gardens and waste places, but is ea,sily eradicated. The disease is not of economic importance. Review of Literature. Australian Records. No mention of a leaf and stem spot disease of E. peplus was made by Cooke (1892) or by McAlpine (1895). The disease was noted by Waterhouse (unpublished data) in June, 1921, in the Sydney area. Pieces of material collected by him and embedded in wax in 1921 are filed at Sydney University. Also filed are pieces of diseased material in wax from a collection made in July, 1932, again from the Sydney area. A record of a Septoria leaf spot disease of E. peplus was made by Noble et al. (1934), without either date or locality of occux'rence. The herbarium specimen lodged at the Department of Agriculture, Sydney, is also without date of occurrence, locality or collector's name. A Septoria species is recorded occurring on E. peplus in Brittlebank's catalogue of Australian Fungi (unpublished), compiled between 10th May, 1937, and 2nd March, 1940, but no indication of the date or locality is given, and no specimen is filed in the herbarium.* Overseas Records. Diseases caused by six species of Septoria and two species of Rhabdospora were recorded by Saccardo (1884, 1892, 1913)), on eight species of Euphorbia, but none on E. peplus. Oudemans (1921) listed species of Septoria, Phleospora and Rhabdospora on various Euphorbia species in Europe, but none on E. peplus. No Septoria was recorded for any Euphorbia by Grove (1935), although a Rhabdospora was noted on one species of Euphorbia in Britain. * Personal communication from Mr. S. Fish, Government Biologist, Department of Agri-culture, Victoria.