The effects of seed mass and fluctuating temperatures on the germination and heterotrophic seedling development of 3 seed sources of Russian wildrye, Psathryrostachys juncea (Fisch. Nevski, were studied. Seeds that weighed 2.4, 3.0, 3.6, and 4.2 +/- 0.1 mg of each seed source were germinated in an unlighted incubation chamber at 5-10 degrees C, 5-15 degrees C, 10-15 degrees C, and 10-20 degrees C. Germination and heterotrophic seedlings development were assessed using: 1) mean time to germinate (T-1), 2) the mean proportion of seeds to germinate (G) and 3) mean maximum radicle and coleoptile extension. Data were analyzed using a 4 X 4 X 3 factorial analysis of variance (n=144) comprised of main effects, temperature (T), seed mass (M), and seed source (S)...