SUMMARY A taxonomic scoring method is used to classify the edible bananas and to provide evidence on their evolution. Edible diploid forms of Musa acuminata are thought to be the primary source of the whole group to which another species, M, baibisiana, has contributed by hybridization. Thus there exist diploid and triploid edible forms of M. acuminata and diploid, triploid and tetraploid hybrid types of genetic constitutions that vary according to their histories. There is a faint possibility that a third wild species has contributed to the origins of a small group of triploid hybrid types. Triploidy was probably established under human selection for vigour and fruit size; tetraploidy is inexplicably rare. The centre of origin of the group is Indo‐Malaya and Malaya is probably the primary centre. The two Ldnnaean species M. paradisiaca and M. sapientum refer to identifiable edible varieties which are both shown here to be of hybrid origin. The names therefore may be rejected from the nomenclature of the wild bananas.

An analysis of published data on genetic relations between dry grain yields (y, t ha-') and protein content Cp, protein as a fraction (g g-I) of dry grain] of cereals is presented. In all, 106 usable regressions of y on p across geneotypes were assembled. The long-recognised negative relation between yield and protein concentration was fully substantiated. There is a strong positive relation between grain yield and protein yield. The linear regression coefficient of yield on protein concentration is related to yield, with slope about -15. This relation holds approximately over all cereals. The data can be used to estimate a characteristic parameter described by C = dy/d(yp) = -15-25 at the mean of each experiment. The relationship is surprisingly consistent but no simple physiological interpretation is available. In discussion, the high C, the impact of strong negative regressions of y on p for breeding strategies, the fact that protein yield increases with gross grain yield but at falling p and certain socio-economic consequences are emphasized. An acute need for orderly reporting of experimental data is also emphasised; the existing literature is chaotic as to units, moisture contents and conversion factors.

THE two crops chosen for discussion are superficially very different and yet are botanically surprisingly similar and they pose comparable nomenclatural problems. Both are well enough understood genetically that rational systems of classification can be constructed ; by ' rational ' I mean systems that reveal the evolutionary facts as they are presently understood and yet are sufficiently flexible to admit new findings and changed interpretations without nomenclatural upheaval. I argue that formal botanical nomenclature, which started and froze in pre-genetical times, is a major barrier to understanding such complex groups as the bananas and the potatoes. I do not argue here (though the view is tenable) that formal nomenclature is incompetent also to subsume the facts of taxonomy of wild plants. Wild plants are so numerous and so poorly understood in comparison with the cultigens that, as a matter of practical politics, major changes in taxonomic procedure are inconceivable at the present time. (Which is not to say that significant minor changes would not be both possible and desirable.)The evolution and classification of the cultivated bananas and potatoes are reviewed elsewhere and the facts need not (indeed, cannot) be repeated here (Simmonds, 1959(Simmonds, , 1962, for the bananas: Dodds, 1962, for the potatoes). Comparison shows that the crops resemble each other in three significant respects :-in both, the basic evolutionary steps took place at the diploid level from wild diploid ancestors ; and, in both, diploidy was followed by the human selection of autopolyploidy and of interspecific hybridity. There are also two significant differences :-in the bananas, triploids and hybrids are relatively far more important than they are in the potatoes where, viewed broadly, autotetraploids tend to predominate ; and the crops differ also in the frequency of sexuality, the bananas (having been selected for seed sterility) presenting, in the main, unchanged clonal phenotypes, while the potatoes, under pressure of human selection (and, probably, virus infection), have been much more frequently propagated by new zygotes. This capacity for selective shift of whole potato populations is, indeed, at the root of the major nomenclatural problem presented by the group.The nomenclatures of the bananas and potatoes are profoundly confused. A full discussion is quite impossible here ; it must suffice to refer to a few of the salient facts. First, consider the bananas. The Linnaean names Musa paradisiaca and M . sapimtum can both be referred (with confidence) to known West Indian cultivars so (unlike the situation in the potatoes) there is no doubt of typification. The two cultivars in question are both interspecific hybrid triploids having the genome constitution AAB ; they thus do not represent ' species ' in any reasonable sense of the word and the Linnaean names, if they are to be used at all, cannot accurately be applied to any banana not of the same genetic constitution. Nevertheless they have been used in various combinati...

Regressions of yields of cultivars upon means of sets of cultivars over diverse environments are often used as measures of stability/adaptability. Prolonged selection for performance in environments of high yield potential has generally led to unconscious selection for high regressions. If adaptation to poor environments is required (as it often is in Third World agriculture), common sense suggests that low regressions could be exploited for the purpose. Simulations show that systematic selection in the poor environment is required, not merely trials of potential cultivars after selection in a good environment. In effect, systematic exploitation of a GE interactions effect is proposed. The effects are large enough to reduce correlated responses in different environments to zero. Orderly experimental studies are needed but not available. What information there is does not disagree with the theory developed here.

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