Seed physical and chemical characteristics, germination, seedling development, and establishment of two seed sources of the Eurasian bunchgrass, Psathyrostachys juncea (Fisch.) Nevski, were investigated in the laboratory, growth chamber, and field. Seed sources tested were Vinall, the commercial standard cultivar, and a newly developed strain, Syn-A. Seed mass classes, used for most investigations, were 2.4, 3.0, 3.6, and 4.2 mg. Seeds were dark-germinated under four temperature regimes: 5-10, 5-15, 10-15, and 10-20$\sp\circ$C on 12h-12h cycles. Planting depths were 1, 2, 4, and 6 cm.

Syn-A had heavier mean seed mass than Vinall. Heavy seeds were physically larger, had thicker seed coats, higher nitrogen contents, and lower surface to volume ratios than light seeds. Germination lagtime was not influenced by seed mass; however, cumulative germination increased with seed mass. In evaluating cumulative germination, the Weibull function was a better descriptor of germination than the logistic function. Maximum extension of the radicle and coleoptile increased with seed mass during the heterotrophic phase of early seedling development. In a glasshouse study, seedlings of heavy seeds emerged earlier and produced larger plants, i.e., longer roots and shoots, greater biomass, and deeper rooting depths, under well-watered conditions. Deep planting retarded emergence and seedling development. Growth rates also were faster for seedlings of heavy seeds. In a field study, emergence (%) was greater for heavy seeds during 1989 and 1990. Survival curves were not different among seed masses and the earlier advantage of heavy seeds was not apparent by the end of the growing season each year. These investigations demonstrate the usefulness of planting heavy seeds at relatively shallow (recommended) depths to enhance seedling establishment when revegetating rangelands in the Great Basin.