Data on reproductive and vegetative weights of individuals from Apera spica-venti, Datura stramonium, Abutilon theophrasti, Sorghum halepense and Panicum miliaceum were used to test Weiner's (1988) model of linear size-dependent reproductive output in plants. In general, the populations showed strong evidence of linear relationships between reproductive and vegetative weight, particularly where size differences were primarily due to competition. -from Authors