ON THE AUTECOLOGY OP STIPA NITIDA, A STUDY OF A FODDER GRASS IN ARID AUSTRALIA. By T. G. B. Osborn, Professor of Botany, University of Sydney, J. G. Wood, Lecturer in Botany, University of Adelaide, and T. B. Paltridge, Field Officer, C.S.I.R. (Plate xviii; fourteen Text-figures.) [Read 26th August, 1931.] I. Introduction. The genus Stipa belongs to the tribe Agrosticlae of the family Gramineae and different species are found on the plains and arid-steppe regions of both hemi-spheres where they form an important part of the forage. They are commonly termed "Spear grasses" on account of the sharp pointed "seed" which has a long, usually tightly twisted awn. Stipa nitida S. & H. is the common spear grass in South Australia within the area bounded by the 8-inch isohyet. It is the most important fodder grass for sheep and is one much sought after by these animals. The investigation to be described in this paper was undertaken primarily to discover the effect of grazing and enclosure upon this grass, but the work has developed into a more detailed study of the autecology of the species. The research was carried out at the Koonamore Vegetation Reserve (Osborn, 1925), an area of 1260 acres protected by rabbit-and sheep-proof fencing. This reserve is situated in saltbush-plain country in the north-east of South Australia. It forms, together with the laboratory adjacent, the Arid Flora Research Station of the University of Adelaide. Work at the centre was initiated by one of us in 1926. Since March, 1928, it has been carried on with the aid of a grant from the Commonwealth Council for Scientific and Industrial Research. This has enabled the scope of the work to be extended and made k possible to station a Field Officer at the Reserve. The first-named author desires to express his gratitude to the Council for Scientific and Industrial Research for their generous assistance. He also wishes to thank the Council of the University of Adelaide for the facilities afforded him at Koonamore subsequent to his departure to the University of Sydney. The Koonamore Vegetation Reserve is situated about forty miles north of the railway station of Yunta on the Broken Hill-Peterborough line, at an altitude of about 650 feet. The average rainfall at Koonamore Head Station, four miles distant from the Reserve, over a period of forty years, is 8-42 inches. II. The Status and Description of Stipa nitida S. & H. Considerable confusion has surrounded the status of the species in question. It was originally known as Stipa scabra Lindl. var. auriculata J. M. Black, but on revision of the Australian members of the genus (Hughes, 1921) it was found that Stipa scabra Lindl. of Black's "Flora of South Australia" was in reality Stipa
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