Sericea lespedeza seed were obtained from open‐pollinated chasmogamous flowers and from self‐fertilized cleistogamous flowers from both an outcrossed and a caged plant in each of 10 inbred lines. Chasmogamous seed are approximately 20% heavier than cleistogamous seed; thus, the four progenies in each line allowed comparison of both outcrossing and seed size effects. In a greenhouse test seed size superiority averaged nearly 8% for measurements over a 4‐month period; in the field test initial values were similar but disappeared after 2 months. A superiority for outcrossing was apparent in each test only after several weeks, reaching a maximum of 8.5% over the maternal parents at the end of the first growing season in the field. The small increase from outcrossing possibly reflects both a low level of heterosis and a low percent cross‐pollination. Within the 10 lines seed size was significantly correlated with seedling performance; thus selection for seed size involves genetic factors for growth rate other than seed size alone. Both seed size and heterosis require attention of the plant breeder; however, the levels of effects reported here place definite restrictions on progress to be expected and breeding systems to be used effectively.
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W. A. Cope (1966) studied this question.