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II.

In the past, the wheats have been recognized as wheat, rye and barley by the ancients, but although they may have been aware of some of the non-cultivated species named them, later generations have not been able to identify such names. Linnaeus named 28 species which he placed in the genus Triticeae, Elymus, Secale, Hordeum and Aegilops, and then might have one species in the genus Bromus; in modern origin these two represent only 22 biological species. Since his time many taxa have been described from within this group, so that presently we recognize almost 500 taxa of which about 320 seem to be at least recently good biological species. It may be of interest at this stage to mention that of these taxa 338, or almost 70%, are known as to their chromosome number, that the karyotype ideogram has been determined for 226, or 45% of them, and that about 100 of these taxa have taken part in about 300 hybrid combinations that have been analyzed as to their meiosis.

No other tribe or group of comparable size has been so intensely studied.

Here I would like to make a brief methodological deviation before continuing a discussion of the classification of these genera, which since Linnaeus have been periodically lumped into a few or split into numerous genera on various considerations.

The method of approach to a scientific problem of this kind is clearly of extreme importance, as is the philosophical thinking behind the conclusions to be drawn, because they will to a large extent determine the type of discovery made or the clarification foregone. Putting the matter the other way round, the method of approach is itself largely dictated by the type of answer you want to obtain: it is, in fact, a kind of question! Furthermore, the question will alter with time and the progress of discovery: when one method has yielded the main crop of answers that it could be expected to provide, it is time to ask another kind of question, by adopting a new method.

The original approach to plant taxonomy inevitably was descriptive because botanists set out to describe as fully and accurately as possible the variation of plants and the phenomena which they exhibit. This approach