There are conceptual and practical difficulties in measuring the exact shape of fitness-gain curves and sex allocation, and these hamper empirical testing of some of the predictions of sex allocation theory for plants. Nevertheless, our knowledge of the process that shape fitness-gain curves allows us to formulate hypotheses to test predictions of sex allocation theory. One such hypothesis is that plants adjust their gender according to size. The connection between plant size and gender was thought to be generally weak. Recent data, however, suggest that size-dependent sex allocation (SDS) is a common phenomenon in hermaphrodites and other cosexual plants
