Problems of quantitative inheritance have been studied in perennial ryegrass, with variance analysis of amp;#x201C;autumnamp;#x201D; and amp;#x201C;springamp;#x201d; sown, spacedamp;#x2013;planted selfings and diallel cross progenies and clonal propagules of four random plants. Except for the first cut, yields from periodical cuts were positively correlated but the low degree of significance suggested that no one cut can fully represent annual productivity. Tiller numberamp;#X002f; tiller weight relationships proved to be useful for differentiating the parents. These, and mean weight per seed and selfamp;#x2013;fertility figures are discussed from the point of view of evolution of the different types. Dangers of using clones as indicators of environmental influence in genetical trials are pointed out. Heritability estimates were generally low, but the additive genetical effects were relatively high. Genotypeamp;#x2013;environment interactions and consequent shortcomings of the heritability ratio are discussed. Reciprocal differences were of some importance in this material, but no dominance effects were observed. Changes of inbreeding depression were studied in different plants and characters; in spite of differential inbreeding influence, positive correlations were found between selfings and both overall means and maternal means of crosses.
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