( 1 ) In 1957 dry seeds of yellow cosmos (Cosmos sulphureus CAV. ), having few variations in both flower-type and -color, were irradiated by X-rays of 5, 000 r, 10, 000 r and 20, 000 r. Several useful mutants, such as large flower type, "Yaguruma" and double flowers were induced by dosage of 20, 000 r (see Fig. 1).
