Considerable difficulties are encountered in national seed programmes (to improve crop yields) by the excessive number of varieties recommended for cultivation. Many of the varieties recommended can only be grown in restricted areas due to sensitivity to the environment; some are also low yielding. In order to make the multiplication and distribution of high quality seed of good varieties efficient, the total number of varieties should be as low as possible. For example, in Ceylon 208 varieties of rice were grown before the number of recommended varieties was reduced to 14.